Plenary Speakers

  • Gérard MOUROU - We have the honor to announce the plenary talk of Professor Gérard MOUROU, Nobel Prize in Physics 2018, for having revolutionized the physics of lasers. Short bio
  • Dmitry BASOV, Columbia University, USA - "Quantum materials: Insights from THz and infrared nano-optics"
  • Andrea CAVALLERI, MPI Structure an Dynamics of Matter, Hamburg, Germany - "Terahertz josephon plasmonics: controlling quantum excitations of layered superconductors"
  • Daniel DOLFI, Thalès TRT, France - “Building blocks and concepts for THz remote sensing and communications”
  • Kaz HIRAKAWA, Tokyo University, Japan - "Terahertz spectroscopy of individual nanostructures using nanogap electrodes"
  • Heinz-Wilhelm HÜBERS, German Aerospace Center, Berlin, Germany - "High-resolution THz spectroscopy: from lab to space"
  • Jean-Francois LAMPIN, IEMN Lille, France - "Optically-pumped terahertz sources and applications"
  • Emma MACPHERSON, Warwick University, UK - "THz instrumentation and analysis techniques for biomedical research"
  • Pascale ROY, Synchotron Soleil, France - "Enlarging the frontiers of research in the IR/mm range using synchotron radiation"
  • Dmitry TURCHINOVICH, Bielefeld University, Germany - "Terahertz physics of graphene, possibly the most nonlinear material we know"

Monday 2 September 2019


09:00-10:30 - Plenary Sessions - Amphi Lavoisier

Chairperson: Carlo Sirtori

09:00 Mo-Pl-1

Passion Extreme Light

Gerard MOUROU, École polytechnique, Palaiseau, France

09:45 Mo-Pl-2

Enlarging the frontiers of research in the IR/mm range using synchotron radiation

Pascale ROY, Synchotron Soleil, France

10:30-11:00 - Coffee Break

11:00-12:30 - Parallel sessions Mo-AM

11:00-12:30 - Mo-AM-1 - Gyrotron 1 - Amphi Lavoisier

Chairperson: Jinjun Feng

11:00 Mo-AM-1-1
THALES TH1507 140 GHz 1 MW CW Gyrotron For W7-X Stellarator

Alberto Leggieri1; Stefano Alberti2; Konstantinos Avramidis3; Gunter Dammertz3; Volker Erckmann4; Gerd Gantenbein3; Jean-Philippe Hogge2; Stefan Illy3; Zisis Ioannidis3; John Jelonnek3; Jianbo Jin3; Heinrich Laqua4; Francois Legrand1; Christophe Lievin1; Rodolphe Marchesin1; Ioannis Pagonakis3; Tomasz Rzesnicki3; Philippe Thouvenin1; Manfred Thumm3; Robert Wolf4
1Thales Microwave Imaging Sub-systems, France; 2Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Switzerland; 3IHM - Karlsruhe Institute of Technology, Germany; 4Max Planck Institute of Plasma Physics, Germany

The status of the THALES 140 GHz 1 MW CW industrial gyrotron program for the W7-X stellarator is discussed in this paper. The industrial design and performances are briefly discussed with a focus on the tube reliability and endurance. The TH1507 tubes are capable of 1 MW RF CW output power at 140 GHz up to 1800 s. Actually, 9 tubes are running to energize the ECRH of W7-X plant; they can operate with efficiencies up to 44 %. After more than 10 years operation, the 2nd prototype has been opened opened in order to investigate the main physical wear during operation of the tube. This analysis shows an excellent robustness of the tube. It provides a large confidence in the robustness of the future ITER and TCV Thales programs and the upstarting W7-X 1.5 MW tube upgrade

11:30 Mo-AM-1-2
High-efficiency, Long-pulse Operation Of MW-level Dual-frequency Gyrotron, 84/126GHz, For The TCV Tokamak
Stefano Alberti1; Konstantinos Avramidis2; Andrea Bertinetti3; William Bin4; Jeremie Dubray1; Damien Fasel1; Saul Garavaglia4; Jeremy Genoud1; Timothy Goodman1; Jean-Philippe Hogge1; Pierre-François Isoz1; Pierre Lavanchy1; François Legrand5; Blaise Marlétaz1; Jonathan Masur1; Alessandro Moro4; Ioannis Pagonakis2; Miguel Silva1; Ugo Siravo1; Matthieu Toussaint1
1SPC/EPFL, Switzerland; 2IHM, Karlsruhe Institute of Technology, Germany; 3Politecnico Di Torino, Italy; 4Institute of Plasma Physics/CNR, Italy; 5MIS/Thales, France

The first unit of the dual-frequency gyrotron, 84-126GHz/1MW/2s, for the upgrade of the TCV ECH system has been delivered and is presently being commissioned. During a first phase, long-pulse operation (TRF>0.5s) has been achieved and powers in excess of 0.9MW/0.9s and 1MW/1.2s have been measured in the evacuated RF-load at the two frequencies, 84GHz (TE17,5 mode) and 126GHz (TE26,7 mode), respectively. Considering the different rf losses in the experimental setup, the power level generated in the gyrotron cavity is in excess of 1.1MW and 1.2MW, with a corresponding electronic efficiency of 35% and 36%. These values are in excellent agreement with the design parameters and would likely lead to a gyrotron total efficiency higher than 50% in case of implementation of a depressed collector. The gyrotron behavior is remarkably reliable and robust with the pulse length extension to 2s presently only limited by external auxiliary systems.

11:45 Mo-AM-1-3
DEMO-Relevant Gyrotron Research At KIT

Konstantinos Avramidis1; Gaetano Aiello1; Philipp Thomas Bruecker1; Benjamin Ell1; Thomas Franke2; Gerd Gantenbein1; Giovanni Grossetti1; Stefan Illy1; Zisis Ioannidis1; Jianbo Jin1; Parth Kalaria1; Alexander Marek1; Ioannis Pagonakis1; Sebastian Ruess1; Tobias Ruess1; Tomasz Rzesnicki1; Theo Scherer1; Martin Schmid1; Dirk Strauss1; Manfred Thumm1; Minh Quang Tran3; Chuanren Wu1; John Jelonnek1
1Karlsruhe Institute Of Technology, Germany; 2EUROfusion Consortium, Germany; 3École Polytechnique Fédérale de Lausanne, Switzerland

The DEMO-relevant gyrotron research at Karlsruhe Institute of Technology is driven by the European concept for a demonstration fusion reactor (EU DEMO). This paper reports on the recent results of the theoretical and experimental studies towards the development of gyrotrons fulfilling the DEMO needs.

12:00 Mo-AM-1-4
Powerful Continuous-Wave Sub-Terahertz Large-Orbit Gyrotron

Yuriy Kalynov; Vladimir Manuilov; Aleksander Fiks; Nikolai Zavolsky
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Coherent subterahertz radiation is achieved for the first time in the large-orbit gyrotron operating at a higher cyclotron harmonic in the continuous-wave generation regime. A stable generation is achieved in the case of operation at the third and the second cyclotron harmonics at frequencies of 0.394 THz and 0.267 THz with a radiation power of 0.37 kW and 0.9 kW, respectively.

12:15 Mo-AM-1-5
Megawatt-Power Dual Frequency Gyrotrons For Modern Fusion Facilities

Leonid Popov1; Marina Agapova1; Yury Belov1; Alexey Chirkov3; Grigory Denisov2; Alexander Gnedenkov1; Vladimir Ilin1; Igor Kazansky1; Ilya Khailov1; Artem Kuzmin1; Alexander Litvak2; Vladimir Malygin2; Evgeny Sokolov2; Vladimir Zapevalov2; Vadim Miasnikov1; Mikhail Morozkin2; Alexander Lyubimov1; Elena Soluyanova1; Evgeny Tai1; Sergey Usachev1
1GYCOM Ltd, Russian Federation; 2Institute of Applied Physics, Russian Federation

Nearly 20 years ago demand had arisen in the world practice of plasma investigations with gyrotron usage - to have a source of long-pulse microwave radiation with step-tunable frequency at megawatt-power level. Transparency bands of typical modern 1.8-mm single disc diamond output windows are distant at step of ~35GHz. Attempts to build the reliable broad band output window unit capable to provide long-pulse gyrotron multi-frequency operation with much smaller steps has not succeeded yet. In the same time 10 dual-frequency 140/105GHz long-pulse gyrotrons using single disc diamond window successfully run now at megawatt-power level providing ECRH at ASDEX Upgrade and KSTAR facilities.

11:00-12:30 - Mo-AM-2 - Solid State 1 - Petit Amphi

Chairperson: Alexej Pashkin

11:00 Mo-AM-2-1
2D THz Spectroscopic Investigation Of Ballistic Conduction-band Electron Dynamics In InSb
Sarah Houver; Lucas Huber; Elsa Abreu; Matteo Savoini; Steven Johnson
ETH Zurich, Institute for Quantum Electronics, Switzerland

We follow the trajectory of the out-of-equilibrium electron population in low-bandgap semiconductor InSb, using reflective cross-polarized 2D THz time-domain spectroscopy. The 2D THz spectra show a set of distinct features at combinations of the plasma edge and vibration frequencies. We assign these features to electronic nonlinearities, using finite difference time domain simulations, and show that the nonlinear response in the first picoseconds is dominated by coherent ballistic motion of the electrons. We demonstrate that this technique can be used to investigate the landscape of the band curvature near the Γ-point such as anisotropic characteristics in the (100)-plane.

11:30 Mo-AM-2-2
Excitonic Terahertz Emission From Silicon At Steady-State Interband Photoexcitation

Alexey Zakhar'in; Alexander Andrianov
Ioffe Institute, Russian Federation

Converted to poster in the Tuesday Poster Session

11:45 Mo-AM-2-3
Background-free Spectroscopy Of Impurity Transitions In Semiconductors With A Continuous-wave Terahertz Photomixer Source

Martin Wienold1; Sergey G. Pavlov1; Nikolay V. Abrosimov2; Heinz-Wilhelm Hübers1
1German Aerospace Center (DLR), Germany; 2Leibniz-Institut fuer Kristallzuechtung, Germany

We present a method for background-free spectroscopy of shallow impurity transitions in semiconductors with residual impurity concentrations. The method is based on a continuous wave terahertz photomixer source and a scheme for optically modulating the concentration of neutral impurities.

12:00 Mo-AM-2-4
Tunable Stokes Shift In Uniaxially Stressed Silicon With Shallow Donors

Roman Zhukavin1; Sergey Pavlov2; Andreas Pohl3; Nikolay Abrosimov4; Helge Riemann4; Britta Redlich5; Heinz-Wilhelm Hübers2; Valery Shastin1
1Institute for Physics of Microstructures, Russian Federation; 2Institute of Optical Sensor Systems, German Aerospace Center (DLR), Germany; 3Department of Physics, Humboldt-Universität zu Berlin, Germany; 4Leibniz-Institut für Kristallzüchtung, Germany; 5Radboud University Nijmegen, Institute for Molecules and Materials, FELIX Laboratory, Netherlands

Experimental investigations of THz emission from silicon (Si) doped by shallow donors under uniaxial stress along the [001] crystal axis upon selective intracenter excitation by an infrared free electron laser are presented. spectral dependences of Si output integral emission on the pump wavelength and Si laser output terahertz emission spectra have been analyzed. Two mechanisms of stimulated emission have been recognized as inversion-population-based lasing and stimulated Raman scattering. It is shown that uniaxial stress allows to control the Stokes shift and by this the output Raman emission frequency in the active medium. The obtained results demonstrate the feasibility of broad range THz tuning in doped silicon by means of uniaxial stress.

11:00-12:30 - Mo-AM-3 - Metrology - Room 269

Chairperson: François Simoens

11:00 Mo-AM-3-1
Metrology Of Complex Refractive Index For Solids In The Terahertz Regime Using Frequency Domain Spectroscopy
Steven Chick1; Guy Matmon2; Ben Murdin1; Mira Naftaly3
1University of Surrey, Advanced Technology Institute, United Kingdom; 2Paul Scherrer Institute, Laboratory for Micro- and Nanotechnology, Switzerland; 3National Physical Laboratory, United Kingdom

We present a metrological study of a new technique for measuring the complex refractive indices of solids in the THz regime. The technique is widely applicable thanks to requiring only frequency-domain spectroscopy, and is shown to be capable of high accuracy reconstruction of the complex refractive index (RI) spectrum. We quantify the sensitivity to experimental imperfections such as noise, showing that the new technique is more robust than previous methods. We demonstrate the extraction of RI of crystalline Si between 2 -- 20 THz using this method, and comment on the capability to discriminate between absorption and scattering using only a power-transmission measurement.

11:30 Mo-AM-3-2
Comparison Of Waveguide And Free-Space Power Measurement In The Millimeter-Wave Range

Andreas Steiger; Mathias Kehrt; Rolf Judaschke
PTB, Germany

A comparison of waveguide-based and free-space power measurements was carried out in the millimeter-wave range at PTB. The measurements revealed good agreement at 100 GHz of both power scales within their uncertainties. This confirms the consistent realization of SI traceable electronic and photonic power measurements at the national metrology institute of Germany.

11:45 Mo-AM-3-3
Average-Power-Scaling Of Broadband THz Radiation To 50mW

Joachim Buldt; Michael Mueller; Henning Stark; Cesar Jauregui; Jens Limpert
Institute of Applied Physics, Germany

We present on power scaling of broadband THz radiation. By using the two-color gas plasma scheme driven by a state-of-the art, ultrafast, high-average-power fiber laser system an unprecedented to average power of 50 mW. The possibilities for further scaling are discussed.

12:00 Mo-AM-3-4
Nicolson-Ross-Weir Method Using 1-port Network Analyzer For MmW And THz Material Characterization

Seckin Sahin; Niru Nahar; Kubilay Sertel
The Ohio State University, ElectroScience Laboratory, United States

We present a simplified Nicolson-Ross-Weir (NRW) material characterization procedure that employs only a 1-port network analyzer for data collection. This approach is particularly attractive for mmW and THz applications, as it eliminates the need for costlier 2-port measurements which are required in the conventional NRW method. Using two successive calibrations of the measurement port, we calculate the 2-port response of the sample under test. We demonstrate our approach for the WR8.0 waveguide band using a multi-offset-short calibration method. The particular calibration also provides frequency regions of validity as a byproduct of the procedure. Subsequently, the conventional NRW analytic procedure is applied to extract material permittivity and permeability using 2 successive 1-port measurements.

12:15 Mo-AM-3-5
Terahertz Continuous Wave System For Measuring Sub-100-µ M-thick Samples Using Gouy Phase Shift Interferometry

Dahye Choi; Il-Min Lee; Kiwon Moon; Dong Woo Park; Kyung Hyun Park
Electronics and Telecommunications Research Institute (ETRI), Republic of Korea

Terahertz continuous wave (CW) system for measuring sub-100-µm-thick samples using Gouy phase shift interferometry is proposed and demonstrated. When the optical path difference (OPD) of the interferometer is zero, destructive interference pattern is produced. In this case, OPD change induced interference signal change is sensitively detected and can be predicted with calculation. By minimizing the difference between the measured and the calculated signal, thickness of a sample can be determined. Thicknesses of sub-100-?m-thick samples are determined with the 5 % accuracy at 625 GHz.

11:00 -12:30 - Mo-AM-4 - THz Detectors 1 - Room 162

Chairperson: Kaz Hirakawa

11:00 Mo-AM-4-1
A Photomultiplier Tube With Sensitivity In The Entire Terahertz- And Infrared Frequency Range
Simon Lehnskov Lange1; Naoya Kawai2; Peter Uhd Jepsen1
1Technical University of Denmark, Denmark; 2Hamamatsu Photonics K.K., Electron Tube Division, Toyooka factory, Japan

We present here for the first time a photomultiplier tube (PMT), which is sensitive to light in the entire terahertz (THz)- and infrared frequency range. The PMT consists of a meta-material-based photocathode and a dynode electron multiplier system kept under vacuum. The photocathode principle is based on ultrafast electron cold field emission (CFE). This principle makes the PMT sensitive to the electric field of the incident radiation. The PMT therefore gives direct access to a host of characteristics of the incident radiation such as polarization, absolute polarity and absolute peak electric field strength with few-ns time resolution.

11:30 Mo-AM-4-2
Plasmonic Nanocavities For High-Responsivity And Broadband Terahertz Detection

Nezih Yardimci; Deniz Turan; Semih Cakmakyapan; Mona Jarrahi
University of California - Los Angeles, United States

We present a high-responsivity and broadband photoconductive terahertz detector based on a plasmonic nanocavity, which enables high quantum efficiency and ultrafast operation without using short-carrier-lifetime substrates. We experimentally demonstrate that a terahertz time-domain spectroscopy setup employing the presented detector can offer 102 dB dynamic range over 0.1-4.5 THz.

11:45 Mo-AM-4-3
Efficient Terahertz Detection With Perfectly-Absorbing Metasurface

Lucy Hale1; Tom Siday1; Polina Vabishchevich2; Charles Harris2; Ting Luk2; John Reno2; Igal Brener2; Oleg Mitrofanov1
1University College London, United Kingdom; 2Sandia National Laboratories, United States

We demonstrate a unique photoconductive design for terahertz (THz) detection based on a perfectly absorbing, all-dielectric metasurface. Our design exploits Mie resonances in electrically connected cubic resonators fabricated in low-temperature grown (LT) GaAs. Experimentally, the detector achieves very high contrast between ON/OFF conductivity states (10^7) whilst also requiring extremely low optical power for optimal operation (100 μW). We find that the Mie resonances dissipate sufficiently fast and maintain the detection bandwidth up to 3 THz.

12:00 Mo-AM-4-4
Grating-assisted Electro-optic Sampling For Enhanced THz Detection Efficiency.

Alexei Halpin1; Wei Cui1; Aidan W. Schiff-Kearn1; Kashif Masud Awan2; Ksenia Dolgaleva3; Jean-Michel Menard1
1University of Ottawa, Department of Physics, Canada; 2Stewart Blusson Quantum Matter Institute, University of British Columbia, Canada; 3University of Ottawa, University of Ottawa, School of Electrical Engineering and Computer Scie, Canada

The use of nonlinear crystals for detection of THz radiation using electro-optic sampling (EOS) is widespread. Phase-matching typically restricts the bandwidth and detection efficiency for EOS. Here we exploit nanofabrication techniques to etch phase-masks into a <110>-cut GaP crystal, to allow for phase-matched detection THz detection. Our method allows to nearly double the detection bandwidth for the chosen crystal thickness, while also increasing the EOS detection efficiency by approximately 40%. Our method can be easily extended to other nonlinear media, or more complex photonic structures, and is highly applicable for broadband high-sensitivity spectroscopy.

12:15 Mo-AM-4-5
Detection Of THz-waves Using The Photomixing Approach

Florin Lucian Constantin
Laboratoire PhLAM, CNRS UMR 8523, France

The quadratic response to the optical fields and the nonlinear electrical response of a LTG-GaAs photomixer are exploited for detection of THz-waves. The rectification and the heterodyne detection in the THz regime using the photomixing approach are theoretically and experimentally demonstrated.

12:30 Mo-AM-4-6
Development Of Multistage Terahertz Wave Parametric Detector
Hikaru Sakai; Kosuke Murate; Yunzhuo Guo; Kodo Kawase
Nagoya University, Japan

The quadratic response to the optical fields and the nonlinear electrical response of a LTG-GaAs photomixer are exploited for detection of THz-waves. The rectification and the heterodyne detection in the THz regime using the photomixing approach are theoretically and experimentally demonstrated.

11:00-12:30 - Mo-AM-5 - THz TDS 1 - Room 151

Chairperson: Guilhem Gallot

11:00 Mo-AM-5-1
Time-Domain Detection Of The Electric Field And Its Conjugate Variable In Ultrabroadband Electro-Optic Sampling
Philipp Sulzer; Kenichi Oguchi; Jeldrik Huster; Andreas Liehl; Cornelius Beckh; Alfred Leitenstorfer
University of Konstanz, Germany

We demonstrate unambiguous detection of the conjugate variable to the electric field in a time-domain experiment. The polarization change induced by nonlinear mixing of probe and multi-THz fields via the Pockels effect is examined concerning changes in ellipticity and tilting of the polarization ellipsoid. Spectrally resolved measurements yield crucial insights into how sum and difference frequency generation processes shape the electro-optic signal for different detection crystals. This approach enables precise, even simultaneous, measurement of the electric field and its conjugate variable by combinations of different phase biases (lambda/4 and lambda/2) and spectral filtering.

11:30 Mo-AM-5-2
SLD-driven Terahertz Cross-correlation Spectroscopy
Daniel Molter1; Michael Kolano1; Georg von Freymann2
1Fraunhofer ITWM, Germany; 2Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany

Terahertz cross-correlation spectroscopy is a fascinating method to generate signals comparable to those of conventional time-domain spectroscopy but using continuous light. We demonstrate the use of a superluminescent diode to drive a cross-correlation spectroscopy system resulting in a truly continuous terahertz spectrum.

11:45 Mo-AM-5-3
Single-shot Detection Of Terahertz Waveforms Using Non-collinear Time-encoding Technique
Kenichi Izumi1; Kohei Kawana1; Masataka Kobayashi1; Yusuke Arashida2; Jun Takeda1; Ikufumi Katayama1
1Yokohama National University, Yokohama National University, Japan; 2Tsukuba University, Japan

We have developed a new scheme for accurately measuring terahertz (THz) waveforms based on a single-shot method using non-collinear time-encoding technique. In this scheme, THz pulses were focused non-collinearly on a LiNbO3 plate with a Si prism coupler together with chirped sampling pulses, enabling us to spatially separate sum- and difference-frequency components from the detected signals. This new approach -- single-sideband detection of each component -- reduces the waveform distortion, and then improves the temporal resolution of the time-encoding technique.

12:00 Mo-AM-5-4
Jones Matrix Calibration And Determination Of The Precision Of Terahertz Time-domain Polarimetry Based On Spinning E-O Sampling Technique
Kuangyi Xu1; M. Hassan Arbab2
1Stony Brook University, United States; 2Stony Brook University, United States

We have developed a terahertz polarimetry system by applying frequency modulation to electro-optic detection. A hollow-shaft motor rotates the detector crystal and the modulated signal is read by a lock-in-type reading instrument. We characterize the precision of this system to be approximately 1.3 degrees. Furthermore, we calculate the Jones matrix of the optical components to calibrate the systematic error induced by them.

12:15 Mo-AM-5-5
Time-Resolved Optical Pump -THz Ellipsometer Probe Measurements
Bong Joo Kang1; Gregory Gäumann1; Premysl Marsik2; Christian Bernhard2; Thomas Feurer1
1University of Bern, Switzerland; 2University of Fribourg, Switzerland

We present the first optical pump-THz ellipsometer probe setup together with proof of principle measurements carried out on an UHR-silicon wafer. The retrieved time-resolved dielectric properties of NIR-pumped silicon show good agreement with two temperature model simulations.

11:00-12:30 - Mo-AM-6 - QCL 1 - Room 101

Chairperson: Karl Unterrainer

11:00 Mo-AM-6-1
Sub-terahertz Quantum-cascade Laser Source Based On Difference-frequency Generation
Kazuue Fujita; Shohei Hayashi; Akio Ito; Masahiro Hitaka; Tatsuo Dougakiuchi; Tadataka Edamura
Hamamatsu Photonics K.K., Japan

Authors report a sub-terahertz monolithic semiconductor source based on a high power, long-wavelength quantum cascade laser. In order to obtain higher nonlinear susceptibility in the sub-terahertz frequency region, we design long wavelength dual-upper-state active region in which transition dipole moments are substantially increased. A fabricated device with distributed feedback grating produces nearly watt-level infrared output power, and as a result, it exhibits a peak output power of ~20 ÃZ¼W at room temperature, around a frequency of ~700 GHz. Besides, the device produces an output power of 103 ÃZ¼W at 110 K.

11:30 Mo-AM-6-2
High-quality N-type Ge/SiGe Multilayers For THz Quantum Cascade Laser
Monica De Seta1; Michele Montanari1; Chiara Ciano1; Luca Persichetti1; Luciana Di Gaspare1; Michele Virgilio2; Giovanni Capellini3; Marvin Zoellner3; Oliver Skibitzki3; David Stark4; Giacomo Scalari4; Jerome Faist4; Douglas Paul5; Thomas Grange6; Stefan Birner6; Mario Scuderi7; Giuseppe Nicotra7; Oussama Moutanabbir8; Samik Mukherjee8; Leonetta Baldassarre9; Michele Ortolani9
1Università Roma Tre Dipartimento di Scienze, Italy; 2Dipartimento di Fisica "E. Fermi", Università di Pisa, Italy; 3IHP-Leibniz-Instut für innovative Mikroelektronik, Germany; 4Institute for Quantum Electronics, ETH Zürich, Switzerland; 5School of Engineering, University of Glasgow, United Kingdom; 6nextnano GmbH, Germany; 7Istituto per la Microelettronica e Microsistemi (CNR-IMM), Italy; 8École Polytechnique de Montréal, Department of Engineering Physics, Canada; 9Dipartimento di Fisica Università La Sapienza, Dipartimento di Fisica, Italy

We investigate optical and structural properties of n-type Ge/SiGe coupled quantum well systems, to assess the growth capability with respect to QCL design requirements, carefully identified by means of a modelling based on the non-equilibrium Green function formalism.

11:45 Mo-AM-6-3
1.65 THz Spanning Homogeneous THz Quantum Cascade Laser: Comb Operation And Injection Locking
Andres Forrer; David Stark; Martin Franckié; Tudor Olariu; Mattias Beck; Jérôme Faist; Giacomo Scalari
ETH Zürich, Switzerland

A homogeneous THz Quantum Cascade Laser with emission spectra spanning over 1.65 THz in a bi-stable, voltage driven regime is presented. A nearly 1 THz emission spectrum in the stable regime showing a narrow electrical beatnote indicating frequency comb operation is observed. Such a narrow beatnote could then be injection locked to an external RF source with powers low as -55 dBm. Together with the low threshold current density of 115 A/cm-2 this design could lead to octave spanning THz QCL frequency combs.

12:00 Mo-AM-6-4
Si-based N-type THz Quantum Cascade Emitter
David Stark1; Luca Persichetti2; Michele Montanari3; Chiara Ciano3; Luciana Di Gaspare2; Monica De Seta2; Marvin Zöllner4; Oliver Skibitzki4; Giovanni Capellini4; Michele Ortolani5; Leonetta Baldassarre6; Michele Virgilio7; Thomas Grange8; Stefan Birner8; Kirsty Rew9; Douglas Paul9; Jérôme Faist10; Giacomo Scalari10
1ETH Zurich, Switzerland; 2Università di Roma Tre, Italy; 3Università di Roma Tre, Italy; 4IHP-Leibniz-Institut für innovative Mikroelektronik, Germany; 5Università di Roma "La Sapienza", Italy; 6Università di Roma "La Sapienza", Italy; 7Università di Pisa,, Italy; 8nextnano, Germany; 9University of Glasgow, United Kingdom; 10ETH Zurich, Switzerland

Employing electronic transitions in the conduction band of semiconductor heterostructures paves a way to integrate a light source into silicon-based technology. To date all electroluminescence demonstrations of Si-based heterostructures have been p-type using hole-hole transitions. In the pathway of realizing an n-type Ge/SiGe terahertz quantum cascade laser, we present electroluminescence measurements of quantum cascade structures with top diffraction gratings. The devices for surface emission have been fabricated out of a 4-well quantum cascade laser design with 30 periods. An optical signal was observed with a maximum between 8-9 meV and full width at half maximum of roughly 4 meV.

12:15 Mo-AM-2-6-5
Stabilizing A Terahertz Quantum-cascade Laser Using Near-infrared Optical Excitation

Tasmim Alam1; Martin Wienold1; Xiang Lü2; Lutz Schrottke2; Holger T. Grahn2; Heinz-Wilhelm Hübers1
1German Aerospace Center (DLR), Germany; 2Paul-Drude-Institut für Festkörperelektronik, Germany

We demonstrate a technique to simultaneously stabilize the frequency and output power of a terahertz quantumcascade laser. The technique exploits frequency and power variations upon near-infrared excitation and does not require an external terahertz optical modulator. By locking the frequency to a molecular absorption line, we obtain a linewidth of about 260 kHz and root-mean-square power fluctuations as low as 0.03%.

11:00-12:30 - Mo-AM-7 - Gas Spectro. & Sensing 1 - Room 201

Chairperson: Olivier Pirali

09:00 Mo-AM-7-1
High-Precision Mid-Infrared Spectroscopy With A Widely Tuneable SI-Traceable Frequency-Comb-Stabilised QCL
Dang Bao An Tran1; Rosa Santagata1; Mathieu Manceau1; Anne Cournol1; Louis Lecordier1; Berengere Argence1; Olivier Lopez1; Sean K Tokunaga1; Fabrice Wiotte1; Haniffe Mouhamad1; Andrei Goncharov1; Michel Abgrall2; Yann Le Coq2; Hector Alvarez-Martinez2; Rodolphe Le Targat2; Won Kiu Lee2; Dan Xu2; Paul-Eric Pottie2; Anne Amy-Klein1; Benoit Darquie1
1Laboratoire de Physique des Lasers, CNRS-Université Paris 13, France; 2LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, France

We report measurements of absolute frequencies of various polyatomic species around 10 µm, at level of accuracies ranging from 10 Hz to 10 kHz, using a widely tuneable SI-traceable optical frequency comb-stabilized quantum cascade laser.

11:30 Mo-AM-7-2
Gas Spectroscopy At 222 -- 270 GHz Based On SiGe BiCMOS Using A Multi-Pass Ring Cell

Nick Rothbart1; Klaus Schmalz2; Heinz-Wilhelm Hübers1
1German Aerospace Center (DLR), Germany; 2IHP - Leibniz-Institut für innovative Mikroelektronik, Germany

We present broadband gas spectroscopy based on SiGe BiCMOS technology. A bandwidth of about 222 -270 GHz is achieved by a combination of two frequency bands on single transmitter and receiver chips. The antennas of transmitter and receiver for both bands are closely placed on a single chip such that coupling into the same optical system can be realized. We coupled the beams into a compact custom-made multi-pass ring cell with an optical path length of 1.9 m. We demonstrate sensitive gas spectroscopy capabilities by a full bandwidth spectrum of methanol.

11:45 Mo-AM-7-3
Tabletop Terahertz Chemical Sensor For Breath Analysis And Analytical Gas Sensing

Ivan Medvedev1; Daniel Tyree1; Parker Huntington1; Jennifer Holt2; Ajani Ross1; Robert Schueler1; Christopher Neese2; Douglas Petkie3
1Wright State University, Department of Physics, United States; 2The Ohio State University, Department of Physics, United States; 3Worcester Polytechnic Institute, Department of Physics, United States

We report on the design and development of a tabletop THz chemicals sensor capable of detecting a wide range of volatile organic compounds with absolute specificity at a part per trillion (ppt) level of dilution. The system is capable of rapid detection of light volatile compounds and was designed for quantitative analytical gas chemical sensing with specific focus on diagnostic breath sensing

12:00 Mo-AM-7-4
An Integrated Photoacoustic Terahertz Gas Sensor

Mattias Verstuyft1; Elias Akiki2; Benjamin Walter3; Marc Faucher2; Mathias Vanwolleghem2; Bart Kuyken1
1Ghent University, Belgium; 2IEMN Lille, France; 3Vmicro, Belgium

An on-chip transducer of terahertz light, absorbed by a trace gas, to a mechanical motion using photoacoustics is proposed. The silicon chip confines light in an optical cavity, wherein an acousto-mechanical cavity is housed. The concentration of a trace gas can be determined from the amplitude of a membrane's motion. The simulations presented here predict a minimum detectable limit of 1 ppm of methanol for 1 mW of terahertz power.

12:15 Mo-AM-7-5
Broadband Terahertz Heterodyne Spectrometer Exploiting Synchrotron Radiation At Sub-megahertz Resolution

Gaël Mouret1; Joan Turut2; Zachari Buchanan3; Olivier Pirali4; Marie Aline Martin-Drumel4; Pacale Roy5; Francis Hindle1; Sophie Eliet-Barois2; Jean François Lampin2
1Université du Littoral Côte d'Opale, France; 2Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), CNRS, France; 3Department of Chemistry, University of California, United States; 4Institut des Sciences Moléculaires d'Orsay, CNRS, Univ. Paris-Sud, Université Paris-Saclay, France; 5SOLEIL synchrotron, France

A new spectrometer on the AILES beamline of the SOLEIL synchrotron facility to achieve sub-MHz resolution in the THz and far-IR regions is currently being developed. Thanks to a dedicated heterodyne detection by use of a new kind of molecular laser as local oscillator along with a Fast Fourier Transform Spectrometer, several pure rotation absorption lines of H2S and CH3OH around 1.073 THz have been recorded.

12:30-14:00 - Lunch

14:00-16:00 -  Parallel sessions Mo-PM1

14:00-16:00 - Mo-PM1-1 - Gyrotron 2 - Amphi Lavoisier

Chairperson: Stefano Alberti

14:00 Mo-PM1-1-1
Dynamics Of Multimode Gyrotron Locked By Quasi-Monochromatic External Signal
Yulia Novozhilova; Gregory Denisov; Vladimir Bakunin
Institute of Applied Physics RAS, Russian Federation

Oscillation regimes in a multimode gyrotron under the influence of quasi-monochromatic external signal with a frequency close to the operating mode frequency are studied. The calculations were performed for a powerful 170 GHz gyrotron developed at IAP RAS as a perspective prototype for ITER. The parameter regions were found where the frequency of operating mode is locked by external signal and follows the variations in the external signal frequency.

14:30 Mo-PM1-1-2
1.2 THz Second Harmonic Gyrotron With Selective Groove

Ilya Bandurkin; Alexey Fedotov; Andrey Fokin; Mikhail Glyavin; Alexey Luchinin; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

A method of selective discrimination of spurious low-harmonic oscillations in gyrotron operating at a high cyclotron harmonic was experimentally demonstrated in a 1.2 THz second cyclotron harmonic tube at a very high transverse mode TE 58,13. The obtained results prove the feasibility and efficiency of the proposed method of mode selection in the THz frequency range, and may be used in the design of a THz CW gyrotron operating at the third cyclotron harmonic.

14:45 Mo-PM1-1-3
High Power Millimeter Waves Generated By An Overmoded Relativistic Cherenkov-type Oscillator

Jinchuan JU; Juntao HE; Xingjun GE; Junpu LING; Ting SHU
National University of Defense Technology, China

An overmoded relativistic Cherenkov-type high power millimeter wave generator operating in Ka-band has been investigated. The associated particle-in-cell (PIC) simulation and experimental results are presented in this paper. The relativistic electron beam with a peak current of 9.9 kA was generated by a pulsed power accelerator launched at a voltage of 605 kV. The relativistic electron beam was guided by an axial magnetic field of about 1 T and transported through the overmoded slow-wave structure. Typically in experiments, the millimeter wave power radiated in the far field was about 630 MW with a frequency of 32.1 GHz and a pulse width of about 10 ns. The radiation mode was well controlled to be quasi-TM01 mode.

15:00 Mo-PM1-1-4
Long-pulse High-efficiency Relativistic Cherenkov Oscillators At L- And S- Bands

Xingjun GE
College of Advanced Interdisciplinary Studies, National University of Defense Technology, China

This paper presents the mechanism and realization of the long-pulse high-efficiency relativistic Cherenkov oscillators operating at L- and S-bands. In simulation, microwaves centred at 1.53 GHz are generated, with power of 2.4 GW, and efficiency of 38%. By optimizing the scheme of electron beam collection, the phenomenon of pulse shortening is effectively suppressed. In the experiment, microwaves centred at 1.52 GHz are generated, with power of 2 GW, efficiency of 33% and pulse duration above 140 ns. Furthermore, an S-band relativistic Cherenkov oscillator is designed. In simulation, microwaves centred at 3.76 GHz are generated, with power of 3.2 GW, and efficiency of 34%. In the experiment, microwaves centered at 3.75 GHz are generated, with power of 2.5 GW, efficiency of 31%, repetition rate of 20 Hz and pulse duration above 110 ns. In the further experiment, a microwave with pulse duration above 200 ns is generated.

15:15 Mo-PM1-1-5
Mechanisms Of Submillimeter Wave Generation By Kiloampere REB In A Plasma Column With Strong Density Gradients

Andrey Arzhannikov; Vladimir Burmasov; Ivan Ivanov; Petr Kalinin; Sergey Kuznetsov; Maksim Makarov; Konstantin Mekler; Sergey Polosatkin; Andrey Rovenskikh; Denis Samtsov; Stanislav Sinitsky; Vasily Stepanov; Igor Timofeev
Budker Institute of nuclear physics SB RAS, Russian Federation

Project of powerful submillimeter wave generator based on intense interaction of a relativistic electron beam with a magnetized plasma is developed at BINP RAS in collaboration with NSU. In presented experiments, the beam with parameters 0.8 MeV/15 kA/6 ÃfÆ'Ã.½Ãfâ?sÃ,¼s is injected into a plasma column with the density ~ 1015 cm-3. Spectral composition of the emission from the plasma column is studied in the frequency band 0.1 -- 1 THz. In the analysis of the results of our studies we focus on the role of strong plasma density gradients in generation of sub-mm waves.

15:30 Mo-PM1-1-6
THz Cherenkov Oscillator With Surface-Radiating Modes

Eduard Khutoryan1; Sergey Ponomarenko1; Sergey Kishko1; Yoshinori Tatematsu2; Seitaro Mitsudo2; Masahiko Tani2; Alexei Kuleshov1
1O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine; 2Research Center for Development of Far-Infrared Region, Japan

In this paper, we present and discuss some operation modes arising in the oscillator with a sheet electron beam and a periodically modified grating. Special attention has been paid to the modes when surface plasmon polaritons are coupled to the radiating wave. The presented simulation results indicate high potential of the proposed oscillator for an efficient generation of THz radiation.

15:45 Mo-PM1-1-7
Simulation Of Secondary Electrons In A Megawatt-Class Gyrotron Collector With Voltage Depression And Magnetic Sweeping

Stephen Cauffman; Monica Blank; Philipp Borchard; Kevin Felch
CPI, United States

In megawatt-class gyrotrons, the residual energy of the electron beam must be dissipated in the collector without compromising the vacuum integrity of the device, necessitating the use of various methods for lowering the peak power density to acceptable levels. Secondary electron emission from the collector surface can redistribute the power deposition profile of the incident (primary) beam, which can either be beneficial or detrimental. Secondary electrons may also be re-accelerated toward the gyrotron body, and, if not magnetically reflected, may interfere with the operation of the interaction circuit. Here, simulations of a megawatt-class gyrotron collector, including the effects of voltage depression, magnetic sweeping, and secondary/reflected electrons, are presented, to assess the potential impact on gyrotron operation and longevity.

14:00-16:00 - Mo-PM1-2 - Solid State 2 - Petit Amphi

Chairperson: Christine Kadlec

14:00 Mo-PM1-2-1
Unveiling Temperature-Dependent Scattering Mechanisms In Semiconductor Nanowires Using Optical-Pump Terahertz-Probe Spectroscopy
Jessica Boland1; Francesca Amaduzzi2; Sabrina Sterzl3; Heidi Potts2; Gözde Tütüncüoglu2; Laura Herz3; Anna Fontcuberta i Morral2; Michael Johnston3
1University of Manchester, United Kingdom; 2École Polytechnique Fédérale de Lausanne, Switzerland; 3University of Oxford, United Kingdom

Optical-pump terahertz-probe (OPTP) spectroscopy is a powerful, non-contact tool for extracting the electrical conductivity within a material. In this work, we show how OPTP spectroscopy can be used to extract the temperature-dependent electron mobility and photoconductivity lifetime within semiconductor nanowires (NWs), in order to reveal the underlying scattering mechanisms governing carrier transport in these materials.

14:30 Mo-PM1-2-2
Time-Resolved THz Spectroscopy Of Metal-Halide Perovskite Single Crystals And Polycrystalline Thin Films

Chelsea Q. Xia1; Qianqian Lin2; Jay B. Patel1; Adam D. Wright1; Timothy D. Crothers1; Rebecca L. Milot3; Laura M. Herz1; Michael B. Johnston1
1University of Oxford, Clarendon Laboratory, United Kingdom; 2Wuhan University, School of Physics and Technology, Wuhan University, China; 3University of Warwick, Department of Physics, United Kingdom

In this study the photoconductivity and charge-carrier dynamics of the metal-halide perovskite MAPbI3 is investigated via optical-pump-THz-probe spectroscopy (OPTPS). We perform OPTPS on polycrystalline MAPbI3 thin films in both transmission and reflection modes, and demonstrate the consistency of extracted mobility and recombination parameters between the two geometries. Furthermore, we performed OPTP measurement on MAPbI3 single crystal in reflection and compare the mobility and charge recombination dynamics between the polycrystalline thin films and perovskite single crystals. Finally, the consequence of our results for future metal halide optoelectronic devices are discussed.

14:45 Mo-PM1-2-3
The Observation Of Spin Reorientation Phase Transition In Sm1-xErxFeO3

Yohei Koike; Kazumasa Hirota; Hongsong Qiu; Shodai Kimoto; Kosaku Kato; Masashi Yoshimura; Makoto Nakajima
Institute of Laser Engineering, Osaka University, Japan

Through the observation of magnetic resonance modes by terahertz time domain spectroscopy (THz-TDS) at the various temperature, we succeeded in observing spin reorientation phase transition (SRPT) which occurs at 310 K for Sm0.7Er0.3FeO3 single crystals. Furthermore, THz-pump and optical-Faraday-rotation measurement was introduced and the weak F-mode signals were successfully observed just below SRPT temperature.

15:00 Mo-PM1-2-4
Enhanced Generation Of THz Radiation In The Island Films Of Topological Insulators Bi2-xSbxTe3-ySey

Kirill Kuznetsov1; Petr Kuznetsov2; Daniil Safronenkov1; Alexey Temiryazev2; Galina Yakushcheva2; Galiya Kitaeva1
1Lomonosov Moscow State University, Faculty of Physics, Russian Federation; 2Kotelnikov IRE RAS (Fryazino branch)

Using time-domain spectroscopy we studied the topological insulators, Bi2-xSbxTe3-ySey thin films of different thickness and chemical composition. The obtained temporal dependences of terahertz pulses show that generation of THz radiation is more effective in an island film with a total thickness of about tens of nanometers. For the first time an amplification of the THz radiation power by applying an external electric field to a topological insulator is demonstrated. This effect can be useful for fabricating photoconductive antennas based on topological insulators.

15:15 Mo-PM1-2-5
Analysis Of Glass Transition Temperatures In Indomethacin Polymer Mixtures

Adam Zaczek; Axel Zeitler
University of Cambridge, Department of Chemical Engineering and Biotechnology, United Kingdom

While drugs are typically created, stored, and administered in the more stable crystalline state, there is interest in industrial settings to stabilise amorphous pharmaceuticals to overcome bioavailability constraints. Terahertz time-domain spectroscopy (THz-TDS) can be used to determine how the glass transition temperatures directly relate to the stability of an amorphous sample. Indomethacin is an extensively studied anti-inflammatory, providing a benchmark sample for amorphous studies with terahertz spectroscopy. By mixing indomethacin with varying ratios of polymeric matrices, its amorphous stability can be increased, revealing trends in the THz-TDS results that directly relate to the potential energy surface of the system which provides insight into the interactions that occur within amorphous mixtures.

15:30 Mo-PM1-2-6
Coexistence Of Ferromagnetic And Superconducting Domains In Co-doped BaFe2As2 Superconductors Probed Using Infrared Faraday Measurements

Alok Mukherjee1; Murat Arik1; Jungryeol Seo1; Hui Xing1; Payam Taheri1; Hao Zeng1; Igor Mazin2; Hikaru Sato3; Hidenori Hiramatsu3; Hideo Hosono3; John Cerne1
1University at Buffalo, Physics Dept., United States; 2Naval Research Laboratory, United States; 3Tokyo Institute of Technology, Japan

We explore the electronic and magnetic properties of superconducting iron pnictide films by probing their infrared Hall conductivity as a function of function of energy (0.1- 1.3 eV), temperature (10-300 K) and magnetic field (B = 0-7 T). We find hysteretic behavior in the complex infrared Faraday angle, θ_F, at low B over the entire temperature range. At higher B, θ_F is linear in B and we observe a peak in the high B-field slope near 50 K, which may be related to the superconducting Tc of the films.

15:45 Mo-PM1-2-7
THz Driven Dynamics In Mott Insulator GaTa4Se8

Elsa Abreu1; Danylo Babich2; Etienne Janod2; Benoît Corraze2; Laurent Cario2; Steven Johnson1
1ETH Zürich, Switzerland; 2Institut des Matériaux Jean Rouxel, Université de Nantes, France

GaTa4Se8 is a Mott insulator known to exhibit an electric Mott transition, characterized by a drop in electrical resistivity, when an electric field larger than 1 -- 10 kV/cm is applied for a few tens of microseconds using electrodes deposited on the sample. Here, we show that a resistivity drop can be induced in this material within less than a picosecond. These dynamics occur after excitation by a high field THz pump pulse and persist for a few picoseconds, well beyond the duration of the pump pulse.

14:00-16:00 - Mo-PM1-3 - Ultrafast - Room 269

Chairperson: Juliette Mangeney

14:00 Mo-PM1-3-1

Terahertz Pulse Trapping Beyond The Delay-Bandwidth Limit
Nima Chamanara1; Lauren Gingras1; Aidan W. Schiff-Kearn1; Jean-Michel Ménard2; David G. Cooke1
1McGill University, Canada; 2University of Ottawa, Canada

We demonstrate the trapping of a broadband THz pulse in a cavity with dynamic walls created faster than the cavity transit time. The trapping bandwidth and dwell time within the cavity, formed by patterned fs photoexcitation of reflective metallic regions within a silicon filled parallel plate waveguide, is shown to violate the delay-bandwidth limit of a passive resonator.

14:30 Mo-PM1-3-2
Ultrafast Metallization In NbO2 Studied By Pump-probe THz Spectroscopy

Rakesh Rana; J. Michael Klopf; Jörg Grenzer; Harald Schneider; Manfred Helm;
Alexej Pashkin
Helmholtz-Zentrum Dresden-Rossendorf, Germany

Niobium dioxide (NbO2) is an isovalent counterpart of VO2 with a considerably higher transition temperature (TC = 1080 K). We have performed time-resolved optical pump -- THz probe measurements on a NbO2 epitaxial thin film at room temperature. Notably, the pump energy required for the switching into a metastable metallic state is smaller than the energy necessary for heating NbO2 up to Tc providing strong evidence for the non-thermal character of the photoinduced insulator-to-metal transition.

14:45 Mo-PM1-3-3
Ultrafast Dynamics Of Hydroxyl Radical Observed By Its FID Radiation In Magnetic Field

Vitaly Kubarev1; Evgeniy Chesnokov2; Lev Krasnoperov3; Pavel Koshlyakov2
1Budker Institute of Nuclear Physics, Russian Federation; 2Institute of Chemical Kinetics and Combustion, Russian Federation; 3New-Jersey Institute of Technology, United States

Ultrafast dynamics of OH radical was investigated by its Free Induction Decay (FID) signal. In our experiments doublet rotational line of the radical was excited by pulse of free-electron laser. Effect of a magnetic field on polarization of the FID was studied by numerical simulation. Experimental investigations of the magnetic field effect is in progress now.

15:00 Mo-PM1-3-4
Terahertz Spectroscopy To Unveil Intraband Scattering In Photoexcited Graphene

Srabani Kar1; Stephanie Adeyemo1; Ajay Sood2; Hannah Joyce1
1University of Cambridge, United Kingdom; 2Indian Institute of Science, Department of Physics, India

Intraband scattering dynamics of optically excited graphene has been explored by using time resolved terahertz spectroscopy. The results for different forms of graphene in terms of layers, Fermi energy position, hydrogen functionalization have been discussed and explained by using Boltzmann transport theory. It is shown how the short-range and Coulomb scattering play important roles in determining photoinduced terahertz conductivity. Photoexcited bilayer graphene showed transition from negative to positive photo-induced terahertz conductivity in the spectral range 0.5-2.5 THz. It is revealed that short-range scattering plays the most significant role to determine the ultrafast photocondcutivity of graphene at terahertz range. However, at low doping state, Coulomb scattering contribute significantly to the imaginary part of conductivity.

15:15 Mo-PM1-3-5
Nonlinearity Of Ultrafast Anomalous Hall Currents In GaAs

Christoph Dresler; Mark Bieler
PTB-The National Metrology Institute of Germany, Germany

PTB-The National Metrology Institute of Germany, PTB-The National Metrology Institute of Germany, Bundesallee 100, Germany
We induce ultrafast anomalous Hall currents in GaAs by optical femtosecond excitation at various temperatures and magnetic fields. The currents' dynamics is studied by detecting the simultaneously emitted THz radiation. A linear behavior is obtained at room temperature and low magnetic fields. However, at higher magnetic fields and, in particular, at low temperatures, we enter a highly nonlinear regime, in which the current dynamics drastically varies. Most likely, this variation results from different microscopic mechanisms which compete against each other

15:30 Mo-PM1-3-6
THz Response Of Metallic Structures To Femtosecond Laser Pulses

Ivan Oladyshkin; Daniil Fadeev; Vyacheslav Mironov
Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

The talk is devoted to the nonlinear effects in metallic structures (like gratings and nanoparticle arrays) irradiated by intense femtosecond laser pulses. Possible mechanisms of delayed THz response and specific non-quadratic nonlinear regimes of conversion are analyzed. In contrast to previous models, only low-frequency currents inside the metal are considered without involving electron emission and acceleration. Special attention is paid to the role of plasmonic resonances at optical frequency in the enhancement of low-frequency nonlinear response.

15:45 Mo-PM1-3-7
Surface THz Emission From Germanium

Ignas Nevinskas; Ričardas Norkus; Arūnas Krotkus

Center for Physical Sciences and Technology, Lithuania

Terahertz emission from germanium after femtosecond laser pulse excitation is a result of the photo-Dember effect and the built-in surface electric field. The indirect band gap semiconductor is investigated with various excitation wavelengths and different dopant types to differentiate these mechanisms. THz pulse emission is observed even at exciting quanta energies lower than the direct band gap. The azimuthal angle dependences suggest a 3rd order optical nonlinearity.

14:00-16:00 - Mo-PM1-4 - 2D Materials 1 - Room 162

Chairperson: Berardi Sensale Rodriguez

14:00 Mo-PM1-4-1

THz Excited State Level Spacing In Encapsulated Graphene Quantum Dots
Elisa Riccardi; Sylvain Massabeau; Federico Valmorra; Michael Rosticher; Jerome Tignon; Takis Kontos; Sebastien Balibar; Sukhdeep Dhillon; Robson Ferreira; Juliette Mangeney
Laboratoire de Physique de l'Ecole Normale Superieure, France

We report a high-quality encapsulated graphene quantum dot that exhibits stable Coulomb diamonds and excited states with a spacing of 0.5 THz. The quantum dot is connected to a bow tie antenna for measurements under THz illumination. The experimental set-up includes a dilution cryostat operating at temperature T<200mK with optical access at THz frequencies.

14:30 Mo-PM1-4-2
PT-Symmetric Terahertz Photoconductivity In Hg1-xCdxTe

Dmitry Khokhlov1; Akeksei Kazakov1; Alexandra Galeeva1; Aleksei Artamkin1; Ludmila Ryabova1; Sergey Dvoretsky2; Nikolay Mikhailov2; Mikhail Bannikov3; Sergey Danilov4; Sergey Ganichev4
1M.V. Lomonosov Moscow State University, Russian Federation; 2A.V. Rzhanov Institute of Semiconductor Physics of SB RAS, Russian Federation; 3P.N. Lebedev Physical Institute of RAS, Russian Federation; 4University of Regensburg, Germany

We show that the terahertz photoconductivity in Hg1-xCdxTe-based films with the inverted band structure corresponding to the topological phase is asymmetric in magnetic field which may be considered as T-symmetry breaking. Beside that, the photoconductivity is asymmetric for two mirror-symmetric pairs of potential probes which may be treated as P-symmetry breaking. At the same time, the photoconductivity remains intact upon simultaneous swapping of both magnetic field and potential probe couple revealing thus the PT-symmetry.

14:45 Mo-PM1-4-3
Conductivity Measurement Of Graphene On Thin Polymeric Film By Broadband Air-plasma THz Spectroscopy

Binbin Zhou; Qian Shen; Patrick Whelan; Lujun Hong; Peter Jepsen
DTU Fotonik, Technical University of Denmark, Denmark

The sheet conductivity of graphene on thin polymer film can be accurately measured by air-plasma based ultra-broadband terahertz time-domain spectroscopy (THz-TDS). The transmitted THz echo signals are well separated in time due to the short THz pulse duration, and oscillation-free frequency dependent conductivity curves can be obtained.

15:00 Mo-PM1-4-4
Unveiling The Plasma Wave In The Channel Of Graphene Field-effect Transistor
Amin Soltani1; Frederik Kuschewski2; Marlene Bonmann3; Andrey Generalov4; Andrei Vorobiev3; Florain Ludwig1; Matthias M. Wiecha1; Dovilė Čibiraitė1; Frederik Walla1; Susanne C. Kehr2; Lucas M. Eng2; Jan Stake3; Hartmut G. Roskos1
1Goethe University Frankfurt, Germany; 2University of Technology, Dresden, Germany; 3Chalmers University of Technology, Sweden; 4Aalto University, Finland

Coupling an electromagnetic wave at GHz to THz frequencies into the channel of a graphene field-effect transistor (GFET) provokes collective charge carrier oscillations of the two-dimensional electron gas (2DEG) known as plasma waves. Here, we report the very first experimental and direct mapping of the electric field distribution in a gated GFET at nanometer length scales using scattering-type scanning near-field microscopy (s-SNOM) at 2 THz. Based on the experimental results we deduce the plasma wave velocity for different gate bias voltages, which is in good agreement with the theoretical prediction.

15:15 Mo-PM1-4-5
Excitation And Amplification Of The Unidirectionally Propagating Terahertz Plasmon In A Periodical Graphene Structure
Denis Fateev; Ilya Moiseenko; Konstantin Mashinsky; Viacheslav Popov
Kotelnikov Institute of Radio Engineerin and Electronics, Russian Academy of Science, Russian Federation

The amplification of the unidirectionally propagating plasmon modes excited by the incident terahertz wave in a periodical structure with an active graphene is studied theoretically. The amplification of propagating plasmon modes is due to radiative recombination in inverted graphene.

15:30 Mo-PM1-4-6
Experimental Investigation Of Graphene Layers As 2D Nanoelectrode For Continuous Wave Terahertz Generation

Alaa Jumaah; Shihab Al-Daffaie; Oktay Yilmazoglu; Franko Küppers; Thomas Kusserow
Technische Universität Darmstadt, Germany

The 2D photomixer investigation showed enhanced photocurrent for high THz output power. The number of graphene layers' effect directly the electrical and optical properties of the device. Higher transparency of a thinner graphene increased the illuminated effective area to increase the number of the generated carries. However, a thicker graphene is required to carry high current density and enhance the photomixer performance.

15:45 Mo-PM1-4-7
Modulation Behaviors, Conductivities, And Carrier Dynamics Of Single And Multilayer Graphenes

Emine Kaya1; Nurbek Kakenov2; Coskun Kocabas2; Hakan Altan2; Okan Esenturk2
1Middle East Technical Univeristy, Turkey; 2Bilkent University, Turkey

Time domain and time resolved terahertz studies of single- and multi-layer graphene (SLG and MLG) samples and modulator devices will be presented. A high performance up to 100% of modulators were observed with the devices even at very low voltages. High modulation depth over such a broad spectrum and simple device structure brings significant importance toward application of this type of device in THz and related technologies. In addition, conductivities of SLG and MLG devices were also investigated and a change in behavior was observed as the layer thickness increased. The charge carriers dynamics of the samples with pulp fluence and color was also highly interesting.

14:00-16:00 - Mo-PM1-5 - THz TDS 2 - Room 151

Chairperson: Mona Jarrahi

14:00 Mo-PM1-5-1

THz TDS System With 105 DB Dynamic Range Based On Transition Metal Doped InGaAs
Robert Kohlhaas1; Steffen Breuer1; Simon Nellen1; Lars Liebermeister1; Martin Schell1; Mykhaylo Semtsiv2; William Masselink2; Björn Globisch1
1Fraunhofer HHI, Germany; 2Humboldt University Berlin, Germany

A THz time-domain spectroscopy (TDS) system is presented, which uses photoconductive antennas made of iron and rhodium doped InGaAs. Due to the unique combination of ultrashort lifetime and high mobility as well as high resistivity, the transition metal doped InGaAs surpasses the performance of state-of-the-art photoconductors when applied as THz antennas: The presented THz TDS system features a spectral bandwidth of 6.5 THz and a dynamic range of up to 105 dB.

14:30 Mo-PM1-5-2
Comb-locked Frequency-domain Terahertz Spectrometer
Thomas Puppe; Yuriy Mayzlin; Julian Robinson-Tait; Rafal Wilk
TOPTICA Photonics AG, Germany

We introduce a frequency-domain spectrometers (FDS) based on a comb locked optical frequency synthesizer which combines scanning ranges of more than 3 THz at scan rates >300 GHz/s with frequency resolution in the order of 10 kHz. The comb provides a narrow linewidth spectrum which is absolutely referenced to a frequency standard (e.g. GPS). The inherent stability allows for favorable signal-to-noise scaling with measurement time.

14:45 Mo-PM1-5-3
Rapid Thickness Measurement With A SLAPCOPS-based Terahertz TDS System

Michael Kolano; Oliver Boidol; Daniel Molter; Georg von Freymann
Fraunhofer ITWM, Germany

Terahertz time-domain spectroscopy traditionally requires either one mode-locked laser and an external delay line or two mode-locked lasers with a controllable repetition rate difference. Here we demonstrate a polarization-multiplexed single-laser system, which combines the benefits of both approaches without any external delay line. The fiber laser emits two pulse trains with independently adjustable repetition rates, utilizing only one laser-active section and one pump diode. With a standard fiber-coupled terahertz setup, we are able to measure transients with a spectral bandwidth of 2.5 THz and a dynamic range of 50 dB in a measurement time of 1 s. An additional benefit of the underlying concept is the possibility for the rapid measurement of very thick samples usually not possible with traditional single-laser systems.

15:00 Mo-PM1-5-4
Deep Learning Approach For Removal Of Water Vapor Effects From THz-TDS Signals

Mikhail Mikerov; Jan Ornik; Martin Koch
Philipps-University Marburg, Germany

We propose a new very fast technique for the post-measurement removal of the water vapor effect on THz-TDS signals. Due to its very fast execution time and good generalization ability this technique has the potential to become an alternative to performing the measurements under dry atmosphere.

15:15 Mo-PM1-5-5
Terahertz Time-Domain Spectroscopy Up To 20 THz Based On Organic Electro-Optic Crystals

Mojca Jazbinsek1; Tobias Bach2; Uros Puc1; Vincent Michel1; Carolina Medrano2; Peter Gunter2
1Zurich University of Applied Sciences (ZHAW), Switzerland; 2Rainbow Photonics AG, Switzerland

We demonstrate ultrabroadband THz-wave generation and detection in a compact system based on a femtosecond fiber laser at 1560 nm and optical rectification in organic electro-optic crystals DSTMS. Terahertz time-domain spectroscopy with a spectrum extending up to 20 THz with a maximum bandwidth exceeding 70 dB is possible with this system.

15:30 Mo-PM1-5-6
Terahertz Time-domain Magneto-optic Spectroscopy Without The Polarization-resolution Technique

Masaya Nagai; Atsushi Nakane; Hiroyasu Suzukawa; Tomohide Morimoto; Masaaki Ashida
Osaka University, Japan

We propose a simple method for magneto-optic spectroscopy in the terahertz frequency regime without the conventional polarization-resolution technique. It is based on the time-domain reflection spectroscopy and employs circularly polarized terahertz light with magnetic field modulation. We experimentally demonstrate it for an InAs substrate. Our demonstration will help to advance multi-purpose characterization techniques for various semiconductors.

15:45 Mo-PM1-5-7
Characterization Of Thin Film Liquids By Multilayer Structure In THz Time Domain Reflection Spectroscopy

Qiushuo Sun1; Xuequan Chen1; Kai Liu1; Xudong Liu2; Arturo Hernandez-Serrano3; Emma Pickwell-MacPherson3
1the Chinese University of Hong Kong, Hong Kong; 2Shenzhen University, China; 3University of Warwick, United Kingdom

The characterization of thin film liquids is not as straightforward as bulk materials, as it requires accurate control of the thin film thickness and precise measurements of the amplitude and phase of the signals. We propose a multilayer structure for terahertz (THz) time domain reflection spectroscopy (TDRS) characterization of thin film liquids, the equations for this geometry are derived and the water-ethanol mixtures with various concentrations are measured, the refractive indices and absorption coefficients extracted from the proposed geometry and ordinary bulk reflection geometry match well. This work demonstrates that the proposed multilayer structure can be used to extract the optical properties of liquids by using a tiny amount of the sample, it can be potentially applied to characterize valuable biological aqueous solutions in the future.

14:00-16:00 - Mo-PM1-6 - QCL 2 - Room 101

Chairperson: Martin Wienold

14:00 Mo-PM1-6-1

Frequency Noise And Phase-locking Of A Quantum Cascade Laser-pumped, 1.073THz Molecular Laser Using A 1560nm Frequency Comb
Stefano Barbieri1; Jean-Francois Lampin1; Antoine Pagies1; Giorgio Santarelli2; Hesler Jeffrey3; Wolfgang Hansel4; Ronald Holzwarth4
1IEMN - CNRS Laboratory, France; 2Laboratoire LP2N - CNRS, France; 3Virginia Diodes Inc., United States; 4Menlo Systems GmbH, Germany

We report the measurement of the frequency noise power spectral density (PSD) of a THz molecular laser (ML) pumped by a mid-infrared (MIR) quantum cascade laser (QCL). This is obtained by beating the ML frequency with the harmonic of the repetition rate of a 1560nm frequency comb (FC). We find a frequency noise PSD < 10Hz2/Hz (-95dBc/Hz) at 100kHz from the carrier, limited by the noise of the QCL current driver. We also show that it is possible to actively phase-lock the QCL-pumped ML to the FC repetition rate harmonic by controlling the QCL drive current.

14:30 Mo-PM1-6-2
High-resolution Frequency And Phase Control Of A Terahertz Laser
Reshma A Mohandas1; Alwyn Seeds2; Edmund Linfield1; Giles Davies1; Paul Dean1; Lalitha Ponnampalam2; Joshua Freeman1
1University of Leeds, School of Electronic and Electrical Engineering, United Kingdom; 2University College London, School of Electronic and Electrical Engineering, United Kingdom

We report on the high-resolution frequency and phase control of a terahertz (THz) quantum cascade laser (QCL). The 2.0 THz QCL is locked to a stable microwave reference frequency via an all-fibre infrared frequency comb. The frequency of the QCL is controlled by optical injection and the phase is independently controlled by introducing a phase-lock loop that provides electronic feedback to the QCL, forming an optical injection phase locked loop (OIPLL). By implementing this, for a fixed frequency, (1) the phase of the THz QCL relative to the microwave reference frequency can be controlled within a range 0.3Ãfââ?s¬, (2) the linewidth of the locked QCL was <1Hz (instrument limited) (3) the frequency and phase was stabilised for longer timescales.

14:45 Mo-PM1-6-3
Dispersion Measurements Of Terahertz Quantum Cascade Fabry-Perot Cavities And VECSELs

Tudor Olariu; Mattias Beck; Jerome Faist; Giacomo Scalari
ETH Zurich, Switzerland

A method for obtaining the dispersion of terahertz (THz) quantum cascade lasers (QCL) is presented. By measuring the relative phase of the center burst and first satellite peak within the interferogram of a sub-threshold THz QCL emitting cavity inside a Fourier Transform Infrared Spectrometer (FTIR), the electroluminescence spectrum is determined by Fourier Transform and the group velocity dispersion can be calculated. This method is applicable to any QCL -- here shown for Fabry-Perot (FP) ridge laser as well as VECSEL.

15:00 Mo-PM1-6-4
THz Quantum Cascade Lasers Operating Up To 210 K

Martin Franckie1; Lorenzo Bosco1; Mattias Beck1; Elena Mavrona1; Andreas Wacker2; Jerome Faist1
1ETH Zürich, Switzerland; 2Lund Univsersity, Sweden

We present THz QCLs based on two quantum wells per period, designed and optimized with a nonequilibrium Green's function model, which lase up to 210 K cryostat temperature using a dry etched Cu-Cu double-metal waveguide

15:15 Mo-PM1-6-5
THz Quantum Cascade Laser Frequency Combs

Francesco Mezzapesa1; Katia Garrasi1; Valentino Pistore2; Lianhe Li3; A. Giles Davies3; Edmund Linfield3; Sukhdeep Dhillon2; Miriam Vitiello1
1NEST, CNR - Istituto Nanoscienze and Scuola Normale Superiore, Italy; 2Laboratoire Pierre Aigrain, Departement de physique de l'ENS, France; 3School of Electronic and Electrical Engineering, University of Leeds, United Kingdom

We demonstrate THz optical frequency comb (FC) operation based on ultra-broadband, record dynamic range Quantum Cascade Lasers (QCLs) which exploit a heterogeneous active region design to achieve low and flat chromatic dispersion at the center of the gain curve. By implementing a Gires-Tournois Interferometer (GTI), as tightly coupled at one end of the QCL cavity, we provide lithographically-independent control of the free-running coherence properties of such THz-QCL FC and attain wide dispersion compensation regions, where stable and narrow (~3 kHz linewidth) single beatnotes extend over an operation range that is significantly larger than that of dispersion-dominated bare laser cavity counterparts.

15:30 Mo-PM1-6-6
Gain Dynamics In THz QCLs And Its Implication For THz Comb Sources

Christian Georg Derntl1; Dominik Theiner1; Giacomo Scalari2; Mattias Beck2; Jérôme Faist2; Karl Unterrainer1; Juraj Darmo1
1TU Wien, Photonics Institute, Austria; 2ETH Zürich, Institute of Quantum Electronics, ETH Zürich, Switzerland

In this contribution we present investigation of the interactions between the individual quantum cascade sections of a heterogeneous terahertz quantum cascade laser and their role in the stable operation of a broadband gain material. We employed THz-pump/THz-probe time domain spectroscopy (TDS) and reveal the spectrally resolved gain recovery time for each quantum cascade section that has multi-exponential decay character. Obtained results are discussed with respect to a frequency comb formation.

15:45 Mo-PM1-6-7
Self-Mixing Interferometry In Continuous-Wave High Power 1D And 2D QCL Random Lasers Operating At Terahertz Frequencies
Kimberly Reichel1; Simone Biasco2; Teresa Crisci1; Katia Garrasi1; Francesco Mezzapesa1; Miriam Vitiello1
1NEST, CNR-Nano, Italy; 2NEST, Scuola Normale Superiore, Italy

We observe the first evidence of self-mixing in THz frequency quantum cascade random lasers fabricated in both wire and irregularly squared resonator architectures with surface photonic patterns. By reflecting the emitted light back into the laser cavity and changing the external cavity length, we observe the interference fringes within the laser cavity, thereby proving evidence of self-mixing. This paves the way to detectorless speckle-free imaging applications in the far-infrared.

15:45-16:15 - Coffee Break

16:30-18:15 Parallel sessions Mo-PM2

16:30-18:15 - Mo-PM2-1 - Gyrotron 3 - Amphi Lavoisier

Chairperson: Mikhail Glyavin

16:30 Mo-PM2-1-1
Development Of A Second Harmonic Multi-Frequency Gaussian Beam Output Gyrotron FU CW GVII

Yoshinori Tatematsu1; Kyoya Takayama2; Yuto Maeda2; Tatsuya Ueyama2; Taisei Ogura2; Kazuki Nakagawa2; Ryota Kamiya2; Masafumi Fukunari2; Yuusuke Yamaguchi2; Teruo Saito2
1FIR center, University of Fukui, Japan; 2University of Fukui, Japan

A sub-THz second harmonic multi-frequency gyrotron with Gaussian beam output, Gyrotron FU CW GVII, has been developed. This gyrotron was designed to change the frequency stepwise in the range from 270 to 420 GHz. Oscillations of seven second-harmonic modes were successfully observed and Gaussian beam radiations converted from six oscillation modes were observed. Two second harmonic modes; TE65 and TE85; oscillated in a single mode. Even in case of simultaneous oscillation of fundamental modes, radiation beams converted from second harmonic modes can be separated from the fundamental mode beams by making use of the different radiation directions emitted from the gyrotron window.

17:00 Mo-PM2-1-2
ECRH With 10 Gyrotrons At W7-X -- Achievements And Enhancements

Harald Braune; H.P. Laqua; K.J. Brunner; S. Marsen; D. Moseev; F. Noke; F. Purps; N. Schneider; T. Schulz; T. Stange; P. Uhren; F. Wilde; M. Zanini
Max-Planck-Institut für Plasmaphysik, Germany

Electron Cyclotron Resonance Heating (ECRH) was the main heating system during the operation campaign OP1.2b in 2018 of the W7-X stellarator [1]. The steady state capable ECRH system was used for plasma start-up, X-mode and O-mode heating as well as current drive (ECCD). The ECRH plant is equipped with 10 operational 140 GHz gyrotrons and a quasi-optical transmission line, which is operated under standard atmosphere conditions. The achieved plasma parameters with respect to the performance of the ECRH plant and prospective enhancements will be discussed

17:15 Mo-PM2-1-3
A 35GHz 100kW Klystron Amplifier Design

Fang Zhu
Institute of Electronics, Chinese academy of sciences, China

We present the design and modelling of a five-cavity, high-power klystron operating in Ka-band and paced with permanent magnet focusing system. The amplifier is powered by an electron gun operating at a voltage of 40 kV and a total current of 6 A. The circuit is comprised of four single-gap cavities and a three-gap extended interaction output cavity operating in the ?-mode. The main predicted characteristics of the klystron includes a 100 kW peak power at 35GHz, an efficiency of 40% and 42 dB gain.

17:30 Mo-PM2-1-4
Microwave-Band Chirped Pulse Amplification Technique Based On A System Of Helically Corrugated Waveguides

Irina Zotova; Naum Ginzburg; Lev Yurovskiy; Michael Vilkov; Alexander Sergeev; Sergey Samsonov; Alexander Bogdashov
Institute of Applied Physics RAS, Russian Federation

We consider the possible implementation of the Chirped Pulse Amplification (CPA) technique, widely used in optics, for the microwave frequency band. We propose using helically-corrugated waveguides for pulse stretching and compressing as their dispersion properties strongly depend on geometrical parameters. For stretched pulse amplification, a helical-waveguide gyro-TWT can be used as a broadband amplifier. Simulations with parameters of the experimentally realized 30 GHz gyro-TWT show that for a 300 W, 200 ps incident pulse, amplification up to 4 MW (40 dB) can be achieved in this system, while in the linear regime of the same gyro-TWT the output power is only about 250 kW.

17:45 Mo-PM2-1-5

Completion Of The 8 MW Multi-Frequency ECRH System at ASDEX Upgrade
Dietmar Wagner1; Jörg Stober1; Michael Kircher1; Fritz Leuterer1; Francesco Monaco1; Max Münich1; Martin Schubert1; Hartmut Zohm11; Gerd Gantenbein2; John Jelonnek2; Manfred Thumm2; Andreas Meier2; Theo Scherer2; Dirk Strauss2; Walter Kasparek3; Carsten Lechte3; Burkhard Plaum3; Alexander Zach3; Alexander Litvak4; Gregory Denisov4; Alexey Chirkov4; Vladimir Malygin4; Leonid Popov5; Vadim Nichiporenko5; Vadim Myasnikov5; Evgeny Tai5; Elena Solyanova5
1Max-Planck-Institut für Plasmaphysik, Germany; 2Karlsruhe Institute of Technology, Germany; 3Universität Stuttgart, Germany; 4Insitute of Applied Physics, Russian Federation; 5Gycom Ltd, Russian Federation

Over the last 15 years, the Electron Cyclotron Resonance Heating (ECRH) system at the ASDEX Upgrade tokamak has been upgraded from a 2 MW, 2 s, 140 GHz system to an 8 MW, 10 s, dual frequency system (105/140 GHz). Eight gyrotrons were in routine operation during the current experimental campaign. All gyrotrons are step-tunable operating at 105 and 140 GHz with a maximum output power of about 1 MW and 10 s pulse length. The system includes 8 transmission lines, mainly consisting of oversized corrugated waveguides (I.D. = 87 mm) with overall lengths between 50 and 70 meters including quasi-optical sections at both ends. Further improvements of the transmission lines with respect to power handling and reliability are underway.

18:00 Mo-PM2-1-6
High-Gradient Test Results Of W-Band Accelerator Structures

Mohamed Othman1; Julian Picard2; Samuel Schaub2; Valery Dolgashev1; Sudheer Jawla2; Emma Snively1; Bruno Spataro3; Richard Temkin2; Sami Tantawi1; Emilio Nanni1
1SLAC National Accelerator Laboratory, United States; 2Massachusetts Institute of Technology, United States; 3INFN-LNF, Italy

We report high-gradient test results for a 110 GHz single-cell standing wave accelerating cavity powered by a 1 MW gyrotron. The cavity is fed with 10 ns, 100s of kilowatt pulses, and achieved a field gradient up to 225 MV/m.

16:30-18:30 - Mo-PM2-2 - Solid State 3 - Petit Amphi

Chairperson: Manfred Helm

16:30 Mo-PM2-2-1
Terahertz Anomalous Hall Effect In Mn2-xPtSn

Di Liu1; Artem Pronin1; Anastasios Markou2; Claudia Felser2; Martin Dressel1
1Universität Stuttgart, Germany; 2Max-Planck-Institute for Chemical Physics of Solids, Germany

Coherent-source THz spectroscopy was employed for measuring the Faraday rotation angle of Mn2-xPtSn films (x = 0; 0.2). In the THz experiments, we observe clear signatures of an anomalous Hall state, while any indications of the so-called topological Hall effect -- recently observed in these magnetically disordered systems in dc measurements - are absent. This demonstrates that the charge scattering mechanisms, responsible for the two phenomena, possess very different time scales: the anomalous Hall state is governed by the scattering process with the rates above THz frequencies, while the electron interaction, providing the topological Hall, possesses very low characteristic time scales.

17:00 Mo-PM2-2-2
Nonlinear Modulation Of Optical Absorption In Orthoferrites Due To Spin Precession Induced By Intense Terahertz Magnetic Field

Takayuki Kurihara1; Motoaki Bamba2; Tohru Suemoto3
1University of Konstanz, Germany; 2PRESTO, Japan Science and Technology Agency, Japan; 3Toyota Physical and Chemical Research Institute, Japan

We probe the transient change of near-infrared optical absorption in orthoferrites induced by coherent spin precession motion due to intense terahertz (THz) excitation. It has been found that under strong incident THz magnetic field strengths, the time profile of absorption exhibits periodic oscillation that is double the frequency of impulsively excited spin precession. The observed phenomena can be described by dielectric function which involves spin-spin exchange interaction. Our result demonstrates the potential of intense THz magnetic field in observing and controlling the fundamental interactions in magnetically ordered materials.

17:15 Mo-PM2-2-3
Ultrafast Terahertz Magnetometry

Wentao Zhang1; Pablo Maldonado2; Zuanming Jin3; Keno Krewer1; Jacek Arabski4; Guy Schmerber4; Eric Beaurepaire4; Tobias Kampfrath5; Mischa Bonn1; Peter Oppeneer2; Dmitry Turchinovich6
1Max Planck Institute for Polymer Research, Germany; 2Uppsala University, Sweden; 3Shanghai University, China; 4Institut de Physique et Chimie des Matériaux de Strasbourg, France; 5Freie Universität Berlin, Germany; 6Universität Bielefeld, Germany

THz emission spectroscopy is a powerful tool to access ultrafast magnetization dynamics in laser-excited magnetic systems. Here, we demonstrate femtosecond terahertz magnetometry, a method that can be used to rigorously reconstruct the (sub)picosecond-timescale magnetization dynamics in photoexcited ferromagnetic nanofilms from the magnetically-driven THz emission. Considering the propagation of the THz field from the surface of the film to the THz electro-optic sampling unit, we establish the transfer function, which allows us to obtain the ultrafast magnetization dynamics in the laser-excited sample in a calibrated manner.

17:30 Mo-PM2-2-4
Terahertz Pulsed-field Magneto-spectrometer At Room-temperature

Jean-Francois Lampin1; Antoine Pagies1; Stefano Barbieri1; Ludovic Desplanque1; Xavier Wallart1; Jeffrey Hesler2; Oleksiy Drachenko3; Jean Leotin3
1IEMN-CNRS, France; 2Virginia Diodes, United States; 3LNCMI, France

We have developed a compact pulsed-field THz magneto-spectrometer based on a THz molecular laser and heterodyne detection both at room-temperature. The recently developed continuous-wave THz laser uses mid-IR-pumped ammonia as active medium. The receiver is based on a subharmonic mixer pumped by a multiplication chain. A pulsed magnetic field up to 9 T is supplied by discharging a capacitor in a small coil at room-temperature. We demonstrate here the use of this spectrometer by measuring the effective mass of electrons in an InAs/AlGaSb heterostructure at room-temperature.

17:45 Mo-PM2-2-5
Magnon-polaritons In Dysprosium Ferrite

Marcin Bialek; Arnaud Magrez; Jean-Philippe Ansermet
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland

We report on an experimental observation of a coupling of magnons with cavity photons at THz frequencies in an antiferromagnet dysprosium ferrite (DyFeO3). We show that magnon-polaritons can be observed and controlled in antiferromagnets. This brings the existing research on magnon-photon coupling to THz frequencies, because antiferromagnets have their magnetic resonances in this range even without external magnetic fields.

18:00 Mo-PM2-2-6
Magnetoelectric Excitations In Polar Antiferromagnetic Nickel Tellurates Substituted By Mn And Co

Christelle Kadlec1; Stella Skiadopoulou1; Maria Retuerto2; Filip Kadlec1; Fedir Borodavka1; Martin Misek1; Martha Greenblatt2; Stanislav Kamba1
1Institute of Physics CAS, Czech Republic; 2Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, United States

By a combination of infrared, Raman and time-domain THz spectroscopies, we studied spin and lattice excitations in Ni3TeO6 and its isostructural compounds obtained by substitution of Ni with Mn or Co. Low-temperature THz spectra revealed THz-range excitations sensitive to magnetic field; some of them can be assigned to electromagnons.

18:15 Mo-PM2-2-7
Ultrafast Magnetic Response In ε-Fe2O3 Nano Magnet Measured By Terahertz-pump Optical-Faraday-probe Measurement

MAKOTO NAKAJIMA1; Hongsong Qiu1; Shodai Kimoto1; Kosaku Kato1; Yohei Koike1; Masashi Yoshimura1; Kenta Imoto2; Marie Yoshikiyo2; Asuka Namai2; Seiji Miyashita2; Shin-ichi Ohkoshi2
1Osaka University, Japan; 2the university of Tokyo, Japan

Ultrafast magnetic response in epsilon-iron oxide (ε-Fe2O3) nano magnet was measured by terahertz-pump optical Faraday probe measurement. Terahertz excitations induce the extremely fast response of the magnetization. The response time is within 400 fs which corresponds to the time duration of the terahertz pulses.

16:30-18:15 - Mo-PM2-3 - High Fields 1 - Room 269

Chairperson: Jozsef Fulop

16:30 Mo-PM2-3-1

Strong-field THz Nonlinearity On Gold Nanofilms

Tianshu Hong1; Bing Song1; Chen Ouyang3; Baolong Zhang3; Jungang Miao1; Yutong Li2; Xiaojun Wu1 1School of Electronic and Information Engineering, Beihang University, China; 2School of Physical Sciences, University of Chinese Academy of Sciences, China; 3School of Physical Sciences, University of Chinese Academy of Sciences, China

In summary, we show the nonlinearity of strong-field terahertz radiation on gold nanofilms, and propose that this phenomenon can be explained by the terahertz-induced electron delocalization in the gold nanostructures.

17:00 Mo-PM2-3-2
Terahertz-driven Acceleration Of A Relativistic 35 MeV Electron Beam
Morgan Hibberd1; Alisa Healy2; Daniel Lake3; Vasileios Georgiadis1; Elliott Smith4; Oliver Finlay3; Thomas Pacey5; James Jones5; Yuri Saveliev5; David Walsh5; Edward Snedden5; Robert Appleby4; Graeme Burt2; Darren Graham1; Steven Jamison3
1School of Physics and Astronomy & Photon Science Institute, The University of Manchester, United Kingdom; 2Department of Engineering, Lancaster University,United Kingdom; 3Department of Physics, Lancaster University, United Kingdom; 4School of Physics and Astronomy, The University of Manchester, United Kingdom; 5Accelerator Science and Technology Centre, Science and Technology Facilities Council, United Kingdom

We will present the first results from the CLARA research facility at Daresbury Laboratory demonstrating terahertz-driven acceleration of a relativistic 35 MeV electron beam. A polarization-tailored, frequency-tunable, narrowband terahertz source was used to directly excite the longitudinal accelerating mode of a dielectric-lined waveguide structure for collinear phase-velocity-matched THz-electron interaction.

17:15 Mo-PM2-3-3
Generation Of A Few Cycle Terahertz Pulse In Aperiodically Poled Lithium Niobate By Sequence Of Pump Pulses
Yuri Avetisyan1; Ruben Miroyan1; Apet Barsegyan2; Masayoshi Tonouchi3
1Yerevan State University, Armenia; 2Integra Technologies, United States; 3Osaka University, Japan

It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.

17:30 Mo-PM2-3-4
Frequency-and-polarization-controllable High-power THz Wave Generation Using Organic Nonlinear Optical Crystal

Isao Yoshimine; Masatsugu Yamashita; Hiromichi Hoshina; Mikiko Saito; Hiroaki Minamide; Chiko Otani
RIKEN Center for Advanced Photonics, Japan

Arbitrary control of high-power THz polarization and frequency is studied by the numerical calculation based on the coupled wave approach. THz wave generation using organic crystals via optical rectification provides high conversion efficiency. To avoid the limitation of the generated THz field direction which comes from their optical anisotropy, we propose the synthesis of THz wave generated from two crystals whose optical axis are orthogonal each other. By the calculation, the linearly and circularly polarized THz wave generation by changing the time delay of two pump pulses is demonstrated.

17:45 Mo-PM2-3-5
Exceptionally High THz Energy Densities Generated From Organic Crystals Pumped With Mid- Infrared Pulses

Claudia Gollner1; Edgar Kaksis1; Corinne Brodeur2; Valentina Shumakova1; Andrius Baltuska1; Audrius Pugzlys1; Mostafa Shalaby2
1Photonics Institute, TU Wien, Austria; 2Swiss Terahertz Research-Zurich, Switzerland

We investigate THz generation in organic crystals (DAST and DSTMS) by optical rectification of intense Mid-Infrared pulses. The broadband spectrum exceeds several octaves when pumped by 100 fs, 3.9 μm pulses. We report on an extraordinarily high THz energy density and crystal damage threshold > 120 mJ/cm2.

18:00 Mo-PM2-3-6
Towards MJ-level Ultrashort Terahertz Generated By Optical Rectification With A Compact Terawatt Laser

Antoine Courjaud; Jean-Gabriel Brisset; Pierre Sevillano; Emilien Gontier
Amplitude Systemes, France

We report on the development of a compact diode-pumped Terawatt laser for generation of intense Terahertz pulses by optical rectification in LiNbO3. Using a 15mJ compact ultrafast laser already allowed to demonstrate 150µJ Terahertz, with 0,36% conversion efficiency. We report on a laser delivering 250mJ at 50Hz repetition rate and 480fs pulse duration, holding the potential to generate 1mJ-level Terahertz ultrashort in an equivalent setup.

16:30-18:15 - Mo-PM2-4 - 2D Materials 2 - Room 162

Chairperson: Renbin Zhong

16:30 Mo-PM2-4-1

Cavity-mediated Bound Excitons
Erika Cortese1; Linh Ngoc Tran2; Jean-Michel Manceau3; Giorgio Biasiol4; Iacopo Carusotto5; Raffaele Colombelli6; Simone De Liberato1
1University of Southampton, Department of Physics and Astronomy,United Kingdom; 2Universite Paris-Sud, Centre de Nanosciences et de Nanotechnologies, C2N-Orsay, France; 3Univ. Paris-Sud, Centre de Nanosciences et de Nanotechnologies, CNRS UMR 9001,C2N-Orsay, France; 4Laboratorio TASC, CNR-IOM, Italy; 5Universita di Trento, INO-CNR BEC Center and Dipartimento di Fisica, Italy; 6Univ. Paris-Sud, Centre de Nanosciences et de Nanotechnologies,CNR, C2N-Orsay, France

We experimentally demonstrate the existence of bound excitonic resonances in doped quantum wells whose electron and hole are bind by the exchange of virtual cavity photons. The theory predicts that above a certain coupling threshold a novel discrete resonance appears below the ionisation edge. In our case, the ionisation edge corresponds to the onset of the continuum above the QW barriers. This resonance describes a polaritonic excitation: part-photon and part-bound exciton. Using a sample consisting of 13 GaAs/AlGaAs n+-doped semiconductor QWs embedded in a metal / active region / metal grating cavity, we were then able to experimentally observe such a discrete resonance. We thus provided a first demonstration of the existence of a bound state of two charged particles kept together not by Coulomb interaction but by the exchange of virtual cavity photons.

17:00 Mo-PM2-4-2
The Upper Branch Broadening In Ultrastrongly Coupled THz Landau Polaritons

Shima Rajabali; Giacomo Scalari; Janine Keller; Mattias Beck; Jerome Faist
ETH Zurich, Switzerland

We present our investigation on ultrastrong coupling of the Landau level transitions in a two dimensional electron gas to complementary split ring resonator arrays, as a terahertz metasurface. To achieve a higher coupling rate, the capacitive gap of the resonator is reduced systematically. This increment in the coupling rate is expected due to the enhanced vacuum field fluctuations in a smaller volume mode. However, our results indicate that the gap size reduction introduces a broadening in the upper polariton branch below a certain gap width.

17:15 Mo-PM2-4-3
A New Tunable Topological Platform With Terahertz Band Gap: Pb1-xSnxSe

Gauthier Krizman1; Badih Assaf2; Günther Bauer3; Gunther Springholz3; Robson Ferreira1; Gérald Bastard1; Louis-Anne de Vaulchier1; Yves Guldner1
1Ecole Normale Supérieure, France; 2University of Notre Dame, United States; 3Johannes Kepler Universität, Austria

In topological insulator thin films, new states of matter can be generated by hybridizing the massless Dirac states that occur at the topological insulator surface. In this work, we experimentally introduce a platform where this hybridization can be continuously tuned: the PbSnSe topological superlattice. Using magnetooptical transmission spectroscopy on high quality molecular beam epitaxy grown PbSnSe/ PbEuSe superlattices, we demonstrate that the energy gap emerging from this hybridization can be tuned with temperature from 1 to 10 THz. The engineering of topological states is a promising road to achieve photodetection and/or photoemission in the terahertz range.

17:30 Mo-PM2-4-4
Control Of Terahertz Nonlinearity In Graphene By Gating

Hassan A. Hafez Eid1; Klaas-Jan Tielrooij2; Mischa Bonn3; Dmitry Turchinovich1
1University of Bielefeld, Fakultät für Physik, Germany; 2Catalan Institute of Nanoscience and Nanotechnology, Spain; 3Max Planck Institute for Polymer Research, Germany

We study the dependence of the terahertz (THz) nonlinearity of graphene and its temporal dynamics on the free carrier concentration by THz-pump/THz-probe spectroscopy of a gated graphene at room temperature. The strong THz nonlinearity is attributed to electron heating by the driving THz field and shows a drastic dependence on the background electron concentration, demonstrating a wide-range tunability of the THz nonlinearity of graphene.

17:45 Mo-PM2-4-5
Nonlocal Photoresponse In Epitaxial Hg1-xCdxTe Films With The Inverted Band Structure
Aleksei Kazakov1; Alexandra Galeeva1; Alexey Artamkin1; Sergey Dvoretskiy2; Nikolay Mikhailov2; Mikhail Bannikov3; Sergey Danilov4; Liudmila Ryabova5; Dmitry Khokhlov1
1M.V. Lomonosov Moscow State Univ., Faculty of Physics, Russian Federation; 2Rzhanov Institute of Semiconductor Physics, Russian Federation; 3P.N. Lebedev Physical Institute, Russian Federation; 4Regensburg University, Germany; 5M.V. Lomonosov Moscow State University, Faculty of Chemistry, Russian Federation
We present our results on terahertz photoconductivity studied in Hg1-xCdxTe epitaxial films with the inverted energy spectrum (x<~0.16) in the nonlocal (H-bar type) geometry. We show that the terahertz photoresponse demonstrates nonlocality and asymmetry in magnetic field. We discuss the results in terms of a qualitative model that takes into account coexistence of the bulk transport and boundary conductive channels.

18:00 Mo-PM2-4-6
Hot Carrier Recombination Close To The Dirac Point In Graphene-hBN Van Der Waals Heterostructures

Panhui Huang; Elisa Riccardi; Federico Valmorra; Jérôme Tignon; Sukhdeep Dhillon; Bernard Plaçais; Robson Ferreira; Juliette Mangeney
Ecole Normale superieure, France

We investigate the photoconductive regime in graphene-hBN heterostructures close to the Dirac point. We demonstrate recombination lifetimes of non-equilibrium carriers in excess of 30 ps under continuous mid-infrared illumination (i.e. with photon energy below optical phonon energy in graphene). We also demonstrate the onset of an effective recombination channel relying on electron-hyperbolic phonon coupling by increasing bias. This study opens interesting perspectives to exploit graphene-hBN van der Waals heterostructures with long carrier lifetimes for THz lasing and highly sensitive THz photodetection. Our work also paves the way to develop graphene-based sources for phonon polariton optics.

16:30-18:15 - Mo-PM2-5 - Material 1 - Room 151

Chairperson: Adrien Dobroiu

16:30 Mo-PM2-5-1
Optoelectronic Properties Of Tin-Based Hybrid Metal Halide Perovskite Thin Films For Photovoltaics

Rebecca Milot1; Michael Johnston2; Laura Herz2
1The University of Warwick, Department of Physics, United Kingdom; 2University of Oxford, Clarendon Laboratory, UK
Due to their exceptional optoelectronic properties, hybrid metal halide perovskites thin films have shown extraordinary success as active layers in solar cells. One potential drawback of hybrid perovskites, however, is that the highest performing devices are currently based around toxic, lead-containing materials. Although tin is a promising replacement for lead, p-doping in tin-based materials has prevented them from achieving the efficiencies of their lead-based analogues. Using optical-pump/THz-probe spectroscopy and THz time-domain spectroscopy, we compare the intrinsic and extrinsic optoelectronic properties formamidinium tin triiodide thin films and comment on the fundamental limits to charge transport.

17:00 Mo-PM2-5 -2
Improved Terahertz Effective Media Models For Mixtures Of Polar Liquids

Juin W. Zhou; M. Hassan Arbab
State University of New York at Stony Brook, United States

We present two improved mixed media models for solutions of polar liquids in the THz regime. Simple effective media models do not consider intermolecular interactions or hydrogen bond network distributions in polar liquid solutions, and therefore yield inaccurate estimates of the effective dielectric functions. We present two new models: a volumetric modification to the Bruggeman equation and an effective time constant calculation in Debye-like relaxations. Furthermore, we will discuss the limitations of each model in predicting the dielectric functions.

17:15 Mo-PM2-5 -3
Investigation Of Laser-Patterned Silicon Transmittance In The Frequency Range Of 0.1-4.7 THz

Evaldas Svirplys1; Simonas Indrisiūnas2; Heiko Richter3; Andrzej Urbanowicz4; Linas Minkevicius1; Till Hagelschuer3; Gediminas Raciukaitis2; Heinz-Wilhelm Hubers3; Irmantas Kasalynas1
1Center for Physical Sciences and Technology, Terahertz Photonics Laboratory, Lithuania; 2Center for Physical Sciences and Technology, Laser Microfabrication Laboratory, Lithuania; 3German Aerospace Center, Institute of Optical Sensor Systems, Germany; 4Center for Physical Sciences and Technology, Laboratory of Ultrafast Optoelectronics, Lithuania
The dependence of THz transmittance on the surface roughness of differently laser-patterned silicon was investigated in the frequency range of 0.1-4.7 THz. The scattering of THz waves on rough silicon surface was found as the main mechanism that determines optical losses. The impact of silicon processing in ambient air and argon-rich environments on the THz absorption losses was also observed.

17:30 Mo-PM2-5 -4
Retrieving Permittivity Model Parameters For Polar Liquids And Multilayer Systems Through THz-TDS Time-trace Data Analysis

Melanie Lavancier; Sergey Mitryukovskiy; Nabil Vindas; Jean-François Lampin; Romain Peretti
IEMN, CNRS UMR 8520, France

We present new features of the Fit@TDS software for the analysis of polar liquids and multilayer systems. We also show that the modeling of the absorption coefficient of polar liquids can be improved above 2.5THz. Hence, this software will enable us to retrieve the parameters of the models depicting polar liquids. It will help to analyze and compare charges motions, playing an important role in biology and chemistry with such effects as protein solvation. Finally, the implementation of a scattering model will improve the accuracy of the results. These features will be illustrated with THz-TDS experiments on biological samples (sugars, amino acids, enzymes, emulsions).

17:45 Mo-PM2-5 -5
Observation Of Phase Change Of Methane Hydrate Using THz Waves

Keisuke Matsumura; Kei Takeya; Kodo Kawase
Nagoya University, Japan

We observe a phase change of methane hydrate, which is expected to be a new energy resource, using THz Time-Domain Spectroscopy (THz-TDS). In the temperature zone where methane hydrate should be decomposed, an increase in absorption and a shift in time-domain waveform are observed, which seems to indicate that the sample is mutated.

18:00 Mo-PM2-5 -6
Redox Chemistry In Eumelanin

Zarina Gagkaeva1; Konstantin Motovilov2; Vadim Grinenko3; Maxim Savinov4; Lenar Kadyrov2; Alexei Pronin5; Zakhar Bedran2; Elena Zhukova2; Bernard Mostert6; Boris Gorshunov2
1Moscow Institute of Physics and Technology, Russian Federation; 2MIPT, Russian Federation; 3Institute for Solid State and Materials Physics, Germany; 4Institute of Physics of the Czech Academy of Sciences, Czech Republic; 5Prokhorov General Physics Institute of the Russian Academy of Sciences, Russian Federation; 6Department of Chemistry, Swansea University, United Kingdom

Eumelanin is a perspective conductive biomolecular material, which has already been used for making various bioelectronic devices ranging from transistors to batteries. It is known that its conductivity mechanisms are governed by a redox comproportionation reaction. However, most studies devoted to the redox chemistry of eumelanin lack the data on the temperature behavior of its properties. We use broadband dielectric spectroscopy and heat capacity measurements to study the influence of hydration and temperature on eumelanin's conductivity.

16:30-18:15 - Mo-PM2-6 - Instrum. Biology - Room 101

Chairperson: Gun-Sik Park

16:30 Mo-PM2-6-1
An Ultrasensitive Terahertz Microfluidic Chip Based On Fano Resonance Of A Few Arrays Of Meta-atoms

Kazunori Serita; Hironaru Murakami; Iwao Kawayama; Masayoshi Tonouchi
Osaka University, Japan

We present a nonlinear optical crystal-based terahertz (THz)-microfluidic chip with a few arrays of asymmetric meta-atoms for the measurements of trace amount of solutions. A near-field THz emission source that is locally generated in the process of optical rectification at the irradiation spots of fs laser beams induces a high-Q Fano resonance and modifies the resonance frequency of the meta-atoms when the channel between meta-atoms is filled with solutions with different concentrations. Using this chip, we successfully detected attomole order of solute in a less than 100 pL volume of the solution.

17:00 Mo-PM2-6-2
An Optical Instrument For The Submillimeter Spectroscopy Of The Volatile Metabolome

François Bondu1; Goulc'hen Loas1; Ludovic Frein1; Cyril Hamel1; Anthony Carré1; Virginie Daburon2; Françoise Binet2; Guillaume Ducournau3; Jean-François Lampin3
1CNRS, Univ Rennes, Institut FOTON UMR6082, France; 2CNRS, Univ Rennes, ECOBIO UMR 6553, France; 3CNRS, Université Lille 1, IEMN UMR 8520, France

We are designing and realizing an instrument for the spectroscopy of the volatile metabolome of the soil microorganisms. The use of optical telecommunication elements makes it possible to realize a compact source with a wide range of accessible frequencies (100 GHz - 1 THz range; 3-33 cm?¹) with an accuracy of 10? Hz (3.10?? cm?¹), as well as a low bandwidth detection system. The instrument will discriminate among complex polar molecules. We report on the preliminary performances of parts of the source system.

17:15 Mo-PM2-6-3
Towards Broadband THz Spectroscopy And Analysis Of Sub-wavelength-size Biological Samples
Sergey Mitryukovskiy; Mélanie Lavancier; Flavie Braud; Yue Bai; Emmanuel Dubois; Jean-François Lampin; Romain Peretti
IEMN CNRS/Université de Lille, France

We report on our recent progress toward bio-photonic applications of terahertz time-domain spectroscopy. First, we developed a technique for the confinement of broadband terahertz pulses to a sub-wavelength-volume, and will present its applications to study biological samples. Second, we will discuss the analysis of terahertz time-trace data from bio-samples using our Fit@TDS software based on the time-domain optimization algorithm that enables direct fitting of sample parameters. The combination of these (the experimental and the modelling) techniques is a robust tool for terahertz bio-photonics.

17:30 Mo-PM2-6-4
Technique For Recording THz Response From Bio-Tissue

Maksim Fomin1; Konstantin Taranets1; Nikolay Bagraev2; Leonid Klyachkin2; Vladislav Odintsov3; Vyacheslav Bazarbaev4
1Peter the Great St.Petersburg Polytechnic University (SPbPU), Russian Federation; 2Ioffe Institute, Russian Federation; 3St Petersburg Clinical hospital of RAS, Russian Federation; 4ANO CPE "Institute of Mammology", Russian Federation

The results obtained show the promise of further research in the field of recording THz response from biological tissue with the SNS balance device.

17:45 Mo-PM2-6-5
Quantification Of DsDNA Functionalization Efficiency In THz Biosensors

Christian Weisenstein1; Merle Schmeck1; Dominik Schaar2; Anna Katharina Wigger1; Anja Bosserhoff2; Peter Haring Bolívar1
1University of Siegen - High Frequency and Quantum Electronics, Germany; 2Friedrich-Alexander-University Erlangen-Nürnberg, Germany

In the past, THz bioanalytical techniques have been proven to be viable tools for label-free detection of biomolecules. However, significant improvements in the detection limit are needed to apply THz biosensors in biomedical diagnosis. To determine detection limits of the biosensor and the absolute amount of sample volume, quantitative measurements are required. We present label-free THz sensing of dsDNA and implement an approach based on reference investigations to quantify the dsDNA functionalization density. Defined functionalization densities are vital to maximize the adsorption of a dsDNA groove-binding protein, which acts as a tumor marker for malignant melanoma.

18:00 Mo-PM2-6-6
Pressure Controlled In Vivo THz Measurements Of Skin: Monitoring The Effects Of Moisturizers

Hannah Lindley1; A. I. Hernandez-Serrano1; Qiushuo Sun2; Jiarui Wang2; Emma Pickwell-MacPherson1
1University of Warwick, Dpt of Physics, United Kingdom; 2Chinese University of Hong Kong, Dpt of Electronic Engineering, Hong Kong

Pressure is a variable which must be controlled during in vivo skin measurements if comparisons between subjects and measurements are to be obtained. We have built a device to indicate (and record) if the contact pressure between the skin and the imaging window is within the desired range at the time of measurement. Using this device, terahertz (THz) measurements of skin before and after the application of a commercial skin-care product were taken. Significant changes in the THz skin properties were observed, which cannot therefore be attributed to varying contact pressure. These results demonstrate that with a rigorous protocol THz imaging has the potential to be used for testing new skin products and quantifying their effects on the skin and how long these last.

18:15-19:30 - Poster session - Mo-Po 1 - Room 8

Scattering Of THz Radiation By Spherical MWCNTs Aerogel In State Of Acoustic Levitation

Alexander Badin1; Igor Dorofeev1; Grigorii Dunaevskii1; Valentin Suslyaev1; Dmitriy Bodazhkov1; Kseniya Simonova1; Sergey Moseenkov2; Vladimir Kuznetsov2
1National Research Tomsk State University, Russian Federation; 2Boreskov Institute of Catalysis SB RAS, Russian Federation

Recently created aerogel with multi-walled carbon nanotubes (MWCNTs) finds more and more new applications due to its unique properties: optimal weight and dimensional parameters, strength, and electrical conductivity. One of MWCNTs aerogel application may be used as a probe fixed in an acoustic standing wave in a tract of a terahertz spectrometer. Therefore, it is of interest to carry out research of the THz radiation scattering by aerogel. The transmission coefficient measurements at various positions of the aerogel in the beam using a BWO spectrometer at the frequency range 63-124 GHz were made. For levitation of aerogel we use acoustic levitation cell based on local transducers. Average diameter of MWCNTs aerogel was 2.7 mm. The calculation of extinction of ideal conductive balls with a diameter of 2.75 mm (MWCNTs aerogel with a specific conductivity of 103 Sm/m and ideally conductive) was carried out.

FT-ESR Measurements On BDPA By Pulsed ESR Using A Gyrotron As High-power Millimeter Wave Source

Seitaro Mitsudo; Kaishi Kono; Kazuki Dono; Kanata Hayashi; Yuya Ishikawa; Yutaka Fujii
Research Center for Development of Far-Infrared Region, University of Fukui, Japan

Pulsed ESR spectroscopy system was developed using the high-power millimeter wave of gyrotron. The FID signal of stable radicals of BDPA diluted with polystyrene was successfully observed by the quadrature detection method. By Fourier transforming of these FID signals, high resolution FT-ESR spectrum of BDPA was successfully obtained.

The Fundamental Terahertz Mode Of L-Alanine: Strong Narrowing, Greater Symmetry And Small And Non-Uniform Shift As Temperature Is Reduced

Thomas Sanders; Jackson Allen; Matthew Large; Josip Horvat; Roger Lewis
University of Wollonogong, Australia

We have measured the spectrum of L-alanine in the terahertz region over a wide temperature range, from 15 to 300 K. At the lowest temperature, the fundamental line is very sharp, of intrinsic width 0.02 THz (0.8 cm-1). As temperature increases, the line broadens, undergoes a non-uniform red shift, becomes more asymmetrical and decreases in oscillator strength.

Density Of State Of Low-frequency Intramolecular Vibrations For Stiff And Flexible Molecules At Solid Phase

Feng Zhang1; Hong-Wei Wang2; Keisuke Tominaga1; Michitoshi Hayashi2; Tetsuo Sasaki3
1Molecular Photoscience Research Center, Kobe University, Japan; 2Center for Condensed Matter Sciences, National Taiwan University, Taiwan; 3Research Institute of Electronics, Shizuoka University, Japan

Densities of state (DOS) of intramolecular vibrations in optical phonon modes have been quantitatively studied for three oligoglycines. Polycyclic aromatic chain molecules have been used as references. We found that the more flexible backbones of oligoglycines lead to drastically faster growth of intramolecular vibrations with the increase of frequency than the stiffer backbones of polycyclic aromatics do.

Ionic Current In Superionic Conductor Na+ Beta-Alumina Induced By Terahertz Electric Fields

Yasuo Minami1; Benjamin Ofori-Okai2; Prasahnt Sivarajah3; Ikufumi Katayama4; Jun Takeda4; Keith Nelson3; Tohru Suemoto5
1Tokushima University, Japan; 2SLAC National Accelerator Laboratory, United States; 3Massachusetts Institute of Technology, United States; 4Yokohama National University, Japan; 5Toyota Physical and Chemical Research Institute, Japan

We demonstrate that intense terahertz (THz) electric-field transients can manipulate the motion of ions in an ionic conductor. The cations trapped in local potential minima are accelerated by single-cycle THz pulses leading to a macroscopic current flow.

Response Of Strongly Nonequilibrium Plasma Created By High Power Short UV Laser Pulse In Rare Gases To THz Frequency Band Emission

Alexander Popov; Anna Bogatskaya; Ekaterina Volkova
Moscow State University, Russian Federation

The response of plasma created by multiphoton gas ionization in an intense UV laser pulse to the terahertz frequency band radiation is studied. Analysis is based on the Boltzmann equation for the temporal behavior of the electron velocity distribution function (EVDF) in an arbitrary external electric field and allows to take into account both temporal retardation of the EVDF evolution with respect to the external electric field and the effect of the relaxation of the strongly nonequilibrium EVDF due to elastic electron - atomic collisions. The suggested theory enables to properly describe propagation of ultra-short THz pulses in laser plasma waveguides.

Dynamics Of A Sub-terahertz Discharge In The Heavy Noble Gases Produced By A High-density Radiation Field

Alexander Sidorov; Sergey Razin; Alexey Veselov; Mikhail Victorov; Alexander Vodopyanov; Mikhail Morozkin; Mikhail Proyavin; Mikhail Glyavin
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Results of the experimental investigation of the discharge front propagation in the beams of powerful sub-terahertz radiation are presented. The front propagation velocity is measured in the wide range of the gas (argon, krypton) pressure (0.1 -- 1 atm). It is demonstrated that the discharge front runs against the incident sub-terahertz radiation beam into the region with the electric field value well below the threshold. Discharge propagation slowing down in correspondence with the electric field strength decrease. Characteristic propagation velocity value is in the range of 10^5 -- 10^6 cm/s.

A Coherent Smith-Purcell Radiation Source: Design Considerations For A High Power, Tunable Source Of Terahertz Radiation
Huibo Zhang; Ivan Konoplev; George Doucas
John Adams Institute for Accelerator Science, Department of Physics, University of Oxford, United Kingdom

The concept of coherent terahertz (THz) tunable Smith-Purcell radiation source driven by the microbunched electron beam is presented. Studies were performed using numerical and analytical approaches to investigate the radiation generated by electron microbunches. It is demonstrated that the capability of manipulating the microbunching of electron beams results in the possibility to control both the radiation power and the frequency of coherent Smith-Purcell radiation (cSPr). Numerical results were compared with analytical calculations and there is a good agreement between them. These proof of concept studies demonstrate the possibility of designing a high power, broadly tunable THz radiation source.

Modulation Of Terahertz Wave Based On A Preionized Plasma

Liangliang Zhang1; Tong Wu2; Hang Zhao2; Rui Zhang3; Cunlin Zhang1; Yuejin Zhao2
1Capital Normal University, Department of Physics, China; 2Beijing Institute of Technology, China; 3Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China

We demonstrate the modulation of terahertz wave generation from two-color femtosecond laser filament on the basis of a preionized air plasma background created by a modulation pulse using an orthogonal pumping geometry. This is achieved by adjusting and optimizing the phase difference between the two-color laser fields, which is introduced when the two-color fields goes through the preionized air plasma. The results are reasonably coincident with our theoretical simulation based on the plasma photocurrent model. Our results can contribute to the further understanding of the generation mechanism of terahertz wave, enhance the generation efficiency and expand the practical application of terahertz wave.

3-D Calculations Of Terahertz Generation In The Tilted-pulse-front Scheme

Lu Wang; Franz kaertner
DESY, Germany

The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. Thus, a 3D+1 numerical model is necessary for investigating the terahertz generation problem in the tilted-pulse-front scheme. In this article, we compare the differences of the 1D+1, 2D+1 and 3D+1 numerical models. The simulation results suggest a strong spatial dependence on the generated terahertz electric field. The single-cycle pulses are only generated at the neighborhood around the apex of the prism. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments

High Cubic Nonlinearity Of Liquids In The Broadband THz Spectral Range

Maria Zhukova1; Maksim Melnik1; Anton Tcypkin1; Irina Vorontsova1; Sergey Putilin1; Sergei Kozlov1; Xi-Cheng Zhang2
1ITMO University, Russian Federation; 2University of Rochester, United States

Here we report the direct measurement of the nonlinear refractive index coefficient of liquids by using the Z-scan method with broadband pulsed THz beam. The results fit with conventional Z-scan analytics well. We estimate the nonlinear refractive index coefficient n2 of liquids through the use of the theoretical treatment that takes the ionic vibrational contribution into account. This estimation correlates with experimental data obtained.

Intersubband Terahertz Emission From Coupled GaAs/AlGaAs Double Quantum Wells Under Interband Photoexcitation

Alexander Andrianov; Alexey Zakhar'in
Ioffe Institute, Russian Federation

Terahertz range photoluminescence from specially designed structures with tunnel coupled double quantum wells under interband optical excitation has been investigated. A series of narrow emission lines were observed and interpreted as intersubband radiative transitions between electron quantum confinement levels.

Transformation Of The Terahertz Polarization During Three-Wave Joint Propagation In Liquid Nitrogen

Petr Solyankin1; Alexander Shkurinov2; Nikolai Kuzechkin1; Alexei Balakin2; Vladimir Makarov2
1ILIT RAS - Branch of the FSRC «Crystallography and Photonics» RAS, Russian Federation; 2Lomonosov Moscow State University, Russian Federation

In this work we experimentally and theoretically investigate the mutual action of three copropagating waves in isotropic nonlinear medium (liquid nitrogen). Two waves are the first and the second harmonic of the Ti:Sa laser system, and the third one is the terahertz wave generated in the spark of optical breakdown of air. After propagation through liquid nitrogen the change in terahertz polarization state is observed. We attribute this phenomenon to the nonlinear "Terhune-like" mutual rotation of the main axis of a polarization ellipse of terahertz radiation.

Optimization Of Terahertz Source Via An Ambient Air-Based Multi-Color Photoionization

Po-Hsun Wu1; Chan-Shan Yang2; Po-Hsun Chen3; Wei-Che Hu3; Hai-Wei Du4; Xiao-Yu Peng5; Ci-Ling Pan1
1National Tsing Hua University, Taiwan; 2Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taiwan; 3National Tsing Hua University, Taiwan; 4Nanchang Hangkong University, China; 5Center for Terahertz Technology Research, Chongqing Institute of Green and Intelligent Technology, China

By applying the well-known transient current model, theoretically investigating terahertz (THz) emission from gas plasma induced by multi-color femtosecond laser pulses has been developed in this work. Instead of static tunneling ionization model, we adopted Ammosov-Delone-Krainov (ADK) tunneling ionization model to calculate the tunneling ionization rate. In three-color pumping schemes, the optimal power ratio tends to require a larger amount of fundamental field with the increment of total pump power. The optimal relative phases for the 2nd harmonic and 3rd harmonic field are 0.5πand π , respectively.

On The Prospects For The Study Of A Point Discharge Sustained By A Terahertz Free Electron Laser Radiation In An Inhomogeneous Gas Flow

Alexander Vodopyanov
1; Alexander Sidorov1; Alexey Veselov1; Vitaly Kubarev2; Oleg Shevchenko2; Yaroslav Gorbachev2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; 2Budker Institute of Nuclear Physics RAS, Russian Federation

It is proposed to use high-power radiation from a terahertz free electron laser to create a localized (point-like) discharge in an inhomogeneous gas flow. Plasma parameters that can be achieved in such a system open up prospects for creating an effective point-like source of extreme ultraviolet light for the next-generation projection lithography.

High Conversion Efficiency In The System "Nonlinear-Optical Crystal Partially Filling The Cross Section Of A Rectangular Waveguide"

Anahit Nikoghosyan
Yerevan State University, Armenia

It is shown that terahertz radiation (0.1-3 THz) can be effectively generated via optical rectification of femtosecond laser pulses in a system of a "nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide". The numerical calculations for the phase-matching in LiNbO3, ZnTe, DAST and GaSe nonlinear optical crystals have been performed. The influence of THz radiation absorption on the efficiency of generation of coherent THz radiation in the system has been investigated.

Strong Terahertz Electromagnetic Wave Generation Due To Intense Laserplasma Interaction Mechanisms

Andrey Kuratov1; Andrey Brantov2; Yuriy Aliev2; Valery Bychenkov2
1Center of Fundamental and Applied Research, VNIIA, Russian Federation; 2Lebedev Physical Institute RAS, Russian Federation

Strong THz waves have a wide range of applications. Laser -- plasma interaction has advantages over other methods for high power THz generation. We report on our theoretical and numerical investigations of three different mechanisms of THz radiation generation from the laser-plasma sources. We have identified the most effective mechanism of THz pulse generation and quantitatively characterized its properties.

Terahertz Wave Generation Using Single Or Few-Cycle Laser Pulses In A Gaseous Medium

Rajaram Shrestha; Kyung Taec Kim
Gwangju Institute of Science and Technology, Democratic People's Republic of Korea

We perform theoretical calculations to demonstrate that single or few-cycle laser pulses can generate an intense terahertz (THz) emission by a directional current. The THz wave is strongest at the carrier-envelope phase (CEP) of 90 deg. The strength of the THz wave increases as the pulse duration decreases. The results clearly show that the THz wave is maximized when the directional current is maximized.

Nonlinearity In Indium Phosphide Using THz Radiation

Rakesh Kumar Vaddapally1; Chandra vardhan Kotyada1; Kamalesh Jana1; Amit D Lad1; Yash Mukesh Ved1; Shriganesh Prabhu1; Gottfried H Döhler2; Ravindra Kumar Gattamraju1
1Tata Institute of Fundamental Research, India; 2Max Planck Institute for the Science of Light, Germany

Broad band Terahertz(THz) radiation has been used to study the non-linearity in semiconductor materials. The broad band source has been generated using the two color mixing technique from a 20 TW class system. The energy and intensity of the broadband terahertz source which is of the order of microjoules and MV/cm is intense enough to induce non-linearity in the semiconductor. The photon energy of the THz radiation is of the order of meV which is much less than the band gap of the semiconductor materials. Still THz radiation is able to induce nonlinear nature in Indium Phosphide semiconductor. The free carriers are scattered from lowest inter-valley of the semiconductor to the next highest inter-valley of the semiconductor in the conduction band leading to the reduction of overall conductivity of the semiconductor. Thus causing high transmission of THz showing non-linearity in the semiconductor.

Terahertz Generation By Two-color Laser Filamentation

Sarath Maratha Palli1; Philipp Wustelt1; Slawomir Skruszewicz1; Gerhard G Paulus1; Sergey Popruzhenko2; Amrutha Gopal1
1Institut für Optik und Quantenelektronik, Germany; 2Prokhorov General Physics Institute, Prokhorov General Physics Institute, 38 Vavilov str., Russian Federation

Generation of broadband terahertz radiation in air by ionization using two-color femtosecond laser pulses is investigated. Terahertz pulse energy is enhanced by varying the polarization of the laser pulses. We also investigated the influence of phase shift between the femtosecond pulses on the emitted terahertz energy.

Second Optical Harmonic Generation From Interfaces Of Isotropic Materials In Strong Terahertz Field: Surface Vs Bulk Contributions

Sergey Bodrov1; Michael Emelin2; Yuri Sergeev2; Alexey Korytin2; Michael Ryabikin2; Andrey Stepanov2
1University of Nizhny Novgorod, Russian Federation; 2Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

Second optical harmonic generation by nonlinear interaction of femtosecond laser and terahertz pulses in a slab of fused quartz was investigated. It was shown that the second harmonic signal rises only near the slab surfaces and not from the bulk of the fused quartz. The theory of THz induced second optical harmonic in transparent material including dispersion of the optical radiation as well as velocity mismatch of THz and optical pulse was developed. The theory agrees well with experiment.

THz Generation In Laser Filament Under Electric Field Conditions

Valery Losev; Dmitrii Lubenko; Vladimir Prokopev; Sergey Alekseev; Mikhail Ivanov
IHCE SB RAS, IHCE SB RAS, Russian Federation

We present experimental results of generation THz range radiation in a laser plasma. Comparison of one and two-color optical pumping schemes are presented. We report about dependence THz radiation energy from electrical field application point to filament. The maximum generation efficiency is observed when an electric field is applied to geometrical focus point (laser filament is formed from geometrical focus point towards the laser source). The mechanisms of this effect are discussed.

Competition Between Positive And Negative Terahertz Photoconductivity In Variable Thickness Hg1-xCdxTe Epitaxial Layers

Alexandra Galeeva1; Alexey Artamkin1; Alexey Kazakov1; Mikhail Bannikov2; Anton Ikonnikov1; Sergey Dvoretskiy3; Nikolay Mikhailov3; Sergey Danilov4; Ludmila Ryabova1; Dmitry Khokhlov1
1M.V. Lomonosov Moscow State University, Russian Federation; 2P.N. Lebedev Physical Institute, Russian Federation; 3Rzhanov Institute of Semiconductor Physics, Russian Federation; 4Regensburg University, Germany

In this work, we demonstrate that the terahertz photoconductivity in Hg1-xCdxTe epitaxial films (x = 0.13 -- 0.15) is featured by superimposed positive and negative components. The dramatic drop of the positive photoresponse as the sample thickness decreases indicates the crucial role of the bulk carrier contribution to the non-equilibrium transport. However, the photoresponse behavior observed in the magnetic field applied is an argument for an edge phototransport channel formation. We discuss the sign-alternating photoconductivity kinetics in terms of the model that takes into account both the bulk electron excitation and the surface/interface states contribution.

Continuous Wave Microscopy Based On Solid Immersion Lens

Yesenia Angélica García Jomaso1; Naser Qureshi2; Calos Gerardo Treviño Palacios3; Jesús Garduño Mejía2; Rafael Izazaga Pérez3
1Universidad Nacional Autónoma de México, Mexico; 2ICAT-UNAM, Mexico; 3INAOE, INAOE, Mexico

We describe a basic approach of transmission terahertz microscopy based on solid immersion lenses. We use a Backward Wave Oscillator (BWO) as a radiation source, a hyperemispherical silicon lens as solid immersion lens and as a detector a low power pyroelectric. The experimental results show that with this approach we can improve the terahertz spot diameter size of the system compared with a simply aspherical lens. The spot diameter at the focus of the immersion lens is about 0.34 ? at 600 GHz. This approach is extended to an interferometric system to achieve a better sensitivity of the microscope.

Simulation Of A THz Sheet Beam Cyclotron Resonance Staggered Double Grating Traveling Wave Tube

Yu Fan; Zhiqiang Zhang
Institute of electronics, Chinese academy of sciences, China

A Y band cyclotron resonance staggered double-grating traveling wave tube (TWT) is simulated, and a sheet beam with cyclotron electrons is applied to the TWT. Simulation result of the cyclotron resonance enhancement effect is shown. Different ratios of the transverse velocity and longitudinal velocity are compared.

Terahertz Time-Domain Polarimetry Of Carbon Nanomaterials

Anatoly Kvitsinskiy
1; Petr Demchenko1; Alexander Grebenchukov1; Egor Litvinov1; Maxim Masyukov1; Anton Zaitsev1; Ilya Anoshkin1; Anna Baldycheva2; Evgeniya Kovalska2; Anna Vozianova1; Mikhail Khodzitsky1
1ITMO University, Russian Federation; 2University of Exeter, United Kingdom

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a few-layer graphene (FLG) and a randomly oriented single-walled carbon nanotube (SWCNT) thin film on silicon (Si) substrates in terahertz (THz) frequency range under an external optical pumping (OP) and an external static magnetic field (MF). Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse of the samples were obtained experimentally. The results confirm the fact that, based on carbon nanomaterials, it is possible to devise tunable THz polarization modulators for use in the latest security and telecommunication systems.

THz EMI Shielding In Graphene/PMMA Multilayers

Can Koral1; Gianpaolo Papari2; Maria Giovanna Pastore Carbone3; Christos Pavlou3; Costas Galiotis3; Antonello Andreone1
1INFN_National Institute of Nuclear Physics Section of Naples, Italy; 2Department of Physics, University of Naples "Federico II", Italy; 3FORTH/ICEHT Patras, Greece

The electromagnetic interference (EMI) shielding mechanisms of graphene/PMMA multilayered structures are experimentally investigated by using time domain spectroscopy (TDS) in the THz range. Stacked plates of similar thickness (~ 5μm), starting from a single layer up to 100 layers, were produced by a novel approach combining ultra-thin polymer casting and wet deposition techniques. These nano laminates show enhanced electrical conductivity (~ 100 S/cm) and superior specific shielding effectiveness (~ 2-10^4 dB cm² g^-1).

Tri-band Linear To Circular Polarization Converter Based On Transmissive Metasurfaces

Ayesha Kosar Fahad; CunJun Ruan; Tanveer Ul Haq; Shahid Ullah
School of Electronic and Information Engineering, Beihang University, China

Multi-band operation for terahertz wireless systems is a challenging problem. We propose a triple-band linear to circular polarization converter in the Terahertz regime using metasurfaces in transmission modes. The converter is composed of bi-layered metasurfaces separated by a dielectric spacer. Three bands (0.54-0.804, 1.904-2.476, and 2.96-3.884 THz) of linear to circular polarization conversion (LCPC) are achieved due to the superposition of the two transmitted components with a near 90Ã,° phase difference. Idea is verified by finite element method simulation and paves a way to the design of multi-band ransmissive LCPC

Ionic Permeability And Interfacial Doping Of Graphene On SiO2 Measured With Terahertz Photoconductivity Measurements

Hai Wang1; Xiaoyu Jia1; Mischa Bonn1; Klaas-Jan Tielrooij2
1Max Planck Institute for Polymer Research, Germany; 2Catalan Institute of Nanoscience and Nanotechnology (ICN2), Spain

Graphene has been widely used in various electrochemical applications owing to its outstanding electrical and chemical properties. The presence of electrolyte at the graphene surfaces affects graphene's electronic properties, especially its electrical conductivity. The precise mechanism underlying the graphene-electrolyte interaction has remained elusive, despite the importance of graphene for electrochemical applications. Here, we employ optical-pump THz-probe spectroscopy as a contact-free and all-optical means to investigate the impact of cations on graphene conductivity in the electrolyte. We reveal ionic permeability though graphene, resulting in an interfacial doping effect in SiO2-supported graphene.

Temperature Dependent Sheet Conductivity Of MoS2 Measured By Terahertz Time-Domain Spectroscopy

Tao Li; Jun Zhou; Yanshun Zheng; Zheng Zhu; Lin Zhou; Xin Rao; Jun Wang
University of Electronic Science and Technology of China, China

In this work, a typical two-dimensional (2D) material MoS2 has been measured by terahertz time-domain spectroscopy (THz-TDS), and its temperature dependent properties in the temperature range fom 120 K to 500 K have been studied. The transmittance and sheet conductivitiy of monolayer MoS2 have been obtained at different temperatures. This study is useful for the understanding of 2D materials in the THz frequency regions.

Transmission Properties Of Transition Metal Dichalcogenides And Modified Graphene Thin Films In Visible, NIR And THz Frequency Ranges

Maria Zhukova1; Egor Oparin1; Polina Shaban1; Anton Tcypkin1; Ben Hogan2; Evgeniya Kovalska2; Monica Craciun2; Anna Baldycheva2
1ITMO University, Russian Federation; 2University of Exeter, United Kingdom

Here we demonstrate the transmission properties of a thin tungsten disulfide WS2 film fabricated from liquid crystal solutions in near-infrared and THz ranges. These results are compared with other transition metal dichalcogenides transferred to different substrates and unique FeCl3 intercalated graphene-based structures. The introduction of impurities, the selection of structural dimensions and the use of an appropriate substrate for modified 2D layered materials allow controlling the transmission of samples for both the terahertz and infrared ranges, which can be used for the creation of effective modulators and components for THz spectroscopy systems.

Strong Carrier Temperature Dependence Of Complex THz Conductivity of Photo-excited Graphene Due To Electron-phonon Coupling

Masatsugu Yamashita; Sho Ikeda; Chiko Otani
RIKEN, Japan

Ultra-broadband THz conductivities of doped monolayer graphene on PET substrate after photo-excitation at various optical pump fluence are investigated. THz conductivity corresponds to the intra-band transition of hot carriers decreases and deviates from the Drude-type frequency dependence as the pump fluence increases, indicating the broader carrier-energy distribution and energy dependent scattering. However, we found that the semi-classical Boltzmann transport theory with dominant carrier scattering mechanisms such as charged impurity and intrinsic optical phonon scattering with e-ph coupling strength from Density functional theory within GGA approximation failed to explain the hot carrier temperature dependence of THz conductivity spectra. This result suggests that the underestimation of e-ph coupling by DFT calculation and the importance of e-e interaction on the e-ph coupling

Intraband Ultrafast Terahertz Conductivity Dynamics In Graphene

zeyu zhang; Tingyuan Jia
Shanghai Institute of Optics and Fine Mechanics, China

Understanding the subpicosecond carrier dynamics of graphene play a crucial role in its optoelectronic allications. By using various photon energy pump, THz probe spectroscopy, the thermalization dynamics of monolayer graphene was presented. For a doped graphene, the thermal induced intraband terahertz conductivity dynamics shows typically thermal relaxation process in our experiment. The importance of the hot carrier multi-plication process of impurities scattering is discussed for graphene photodetector device applications.

Refractive Index Modulation Induced By High-Intensity THz Radiation

Mohammed Almassarani1; Abel Woldegeorgis2; Takayuki Kurihara3; Amrutha Gopal2
1Helmholtz Institute Jena, Germany; 2Institute of Optics and Quantum electronics, Germany; 3University of Konstanz, Germany

Nonlinear refractive index and absorption coefficient are measured for common semiconductor material such as silicon and organic molecule such as lactose in the terahertz (THz) spectral regime extending from 0.1 to 3 THz. THz pulses with a field strength of 440 MV/m have been employed. Transmittance and the transmitted spectra were measured using Z-scan and single shot noncollinear electro-optic pump-probe techniques. A maximum change in refractive index (Δn) of - 0.128 and +0.245 were measured in lactose and silicon, respectively.

THz Spatial Modulation In The Fourier Plane

Polina Stefanova; Andreas Klein; Claudio Balocco; Andrew Gallant
Durham University, Department of Engineering, United Kingdom

Application of the real-time image processing method of 4F optical systems is presented in the THz regime. Direct manipulation of the Fourier transform of an image through addressable metamaterials is to be explored, in order to achieve THz spatial modulation, beam forming and beam steering.

The Terahertz Near-field Response Of Graphene Layers And Graphene Structures

Valerii Trukhin1; Ilia Mustafin1; Sergey Lebedev1; Anna Baldycheva2
1Ioffe Institute, Russian Federation; 2University of Exeter, United Kingdom

We report on the experimental study of scattering and the near-field interaction of a THz electromagnetic field with graphene layers near the probe of a terahertz near-field microscope. There are resonance lines in the spectrum for a graphene monolayer-based transistor structure, which is possibly due to the strong plasmon response at terahertz frequencies and the manifestation of plasmon interference in the graphene strip.

Sensitivity Measurement Of Resonant-Tunneling-Diode Terahertz Detectors

Yuma Takida1; Safumi Suzuki2; Masahiro Asada2; Hiroaki Minamide1
1RIKEN, Japan; 2Tokyo Institute of Technology, Japan

We report on the performance characterization of resonant tunneling diode (RTD) devices as a terahertz (THz)-wave detector. The frequency-dependent sensitivity of quasi-optical RTD detectors has been calibrated by using a frequency-tunable, sub-ns pulsed THz-wave source. The 0.78-THz, slot-antenna-integrated RTD device shows the peak responsivity of 80 V/W at 0.76 THz with the full-width at half-maximum bandwidth of 70 GHz.

Observation Of Dirac Semi-metallic Topological State In SrIrO3 And CaIrO3 Using Terahertz Time-domain Spectroscopy

Dhanvir Rana; Santhosh Kumar K
Indian Institute of Science Education and Research (IISER) Bhopal, India

Experimental realization of quantum phases such as Dirac and Weyl semimetals, topological insulators and superconductors is an emerging subject of interest in condensed matter physics. In this talk, I will give a brief introduction to Dirac semimetals and theoretical predictions of such ground state in orthorhombic perovskite iridates having strong spin-orbit coupling. I will present the observation of such 3D Dirac semi-metallic ground state in AIrO3 (A = Ca, Sr) thin films using terahertz time-domain spectroscopy.

0.37 THz Gyro-TWA With A Cryo-free SCM: Design And Simulation

Craig Donaldson1; Liang Zhang1; Adrian Cross1; Kevin Ronald1; Alan Phelps1; Wenlong He2
1University of Strathclyde, United Kingdom; 2Shenzhen University, College of Electronic Science and Technology, China

This paper reports the work being carried out to realize a gyrotron-traveling wave amplifier operating at 372 GHz based on a helically corrugated interaction region (HCIR). The high magnetic field will be provided through a cryo-free superconducting magnet. There are many components in the waveguide circuit, which must achieve very low reflection targets. The design and simulation results of the gyro-TWA, the cusp electron beam source, the sub-millimetre wave components, as well as measurement of the HCIR will be presented in this paper.

Recent Results Of A CW, 94 GHz Second Harmonic Gyrotron Based On A Continuous Operation Solenoid

Dimin Sun; Tingting Zhuo; Guowu Ma; Linlin Hu; Hongbin Chen; Fanbao Meng
Institute of Applied Electronics, China Academy of Engineering Physics, China

Recent results of a CW, 94 GHz second harmonic gyrotron with a 1.8 T continuous operation solenoid are presented. The DC solenoid was cooled by water. Its inner bore diameter is 66 mm. The power consumption of the solenoid is 28 kW and the driving current is about 500 A. The gyrating electron beam was generated by a compact triode magnetic injection gun. A high efficiency internal quasi-optical mode converter with a pre-bunch quasi-optical launcher was used to separate the wave from the electron beam. The operating mode of the harmonic gyrotron is TE02. During the CW test, its operational frequency stabilized at 93.9 GHz. In the test, 5 min operation was realized. The output power is 12 kW with an electron beam of 45 kV, 1.6 A. The output efficiency is 24% with a single stage depressed collector.

Optimal Design Of A Magnetron Injection Gun For A 0.5 THz Continuously Frequency-tunable CW Gyrotron

Yanqing Zhang; Wei Wang; Tao Song; Jie Huang; Qiao Hu; Yichao Cao; Chen Zhang; Diwei Liu
UESTC, China

In this paper, the single anode magnetron injection gun with relatively low transverse velocity spread and high velocity pitch factor is designed for a 0.5THz continuously frequency-tunable CW gyrotron.

Electromagnetic Characteristics Of A Double Confocal Waveguide For A Gyro-TWT

Diwei Liu; Chen Zhang; Wei Wang; Tao Song; Qiao Hu; Yichao Cao; Yanqing Zhang
UESTC, China

There are two stable states existing in the double confocal waveguide, which are "superposition mode" and "ring mode". Compared the mode density in the double confocal waveguide with that in the single confocal waveguide and the cylindrical waveguide in the same frequency range, it is obvious that the mode density in the double confocal waveguides is relatively sparse. Hence, the double confocal waveguide has the characteristic of both mode selectivity and efficiency enhancement.

Study Of Low Voltage Angular Log-periodic Slow Wave Structure For 340 GHz TWT

Hexin Wang1; Duo Xu1; Xinyi Li2; Tenglong He1; Zhanliang Wang1; Ruichao Yang1; Tao Tang1; Zhaoyun Duan1; Huarong Gong1; Yanyu Wei1; Yubin Gong1
1University of Electronic Science and Technology of China, China; 2Nanjing Sanle Electronics Group Co., Ltd, China

A novel angular log-periodic groove waveguide slow wave structure (SWS) for 340 GHz traveling wave tube (TWT) is proposed in this paper. Due to the unique characteristics of log-periodic form, the novel SWS could achieve a very low operating voltage and small scale at the same time. By using the groove folded waveguide, the high aspect ratio fan-shaped sheet electron beam could interact with electromagnetic wave in the groove tunnel. According to direct mathematical equation, the operating voltage is 6310 V at 340 GHz and the total length of SWS is 8.6 mm, which could get an output power of 36 W with 20.7 dB gain.

A Novel Millimeter-wave Oversized Coaxial Relativistic Oscillator With Low Guiding Magnetic Field And High Power Capacity

Junpu Ling; Juntao He; Lili Song; Xingjun Ge; Jinchuan Ju; Bingfang Deng
College of interdisciplinary Studies, National University of Defense Technology, China

A novel Millimeter-wave oversized coaxial relativistic oscillator with low guiding magnetic field and high power capacity is proposed. The physical mechanism of this oscillator is investigated by theory and simulation. By introducing a coaxial structure and quasi body wave adopted as the operating mode, the oscillator can run stably under low guiding magnetic. Meanwhile, with an oversized structure and extended interaction extractor operating at higher order mode, the proposed oscillator has the potential of obtaining high output power close to Giggawatt-class. Main structure parameters are optimized by particle in cell simulations. Particle-in-cell simulations show that with the oversized coaxial structure, quasi body wave and extended interaction extractor operating at higher order mode, this proposed oscillator generates a 31 GHz, 840 MW microwave, while the diode voltage is 400 kV, the beam current is 6.1 kA, and the guiding magnetic field is 0.6 T. The corresponding power efficiency reaches 35%.

Terahertz-Infrared Spectroscopy Of Tm0.19Yb0.81B12 Dodecaboride

Elena Zhukova1; Boris Gorshunov2; Andrey Azarevich3; Alexey Bogach3; Volodymyr B. Filipov4; Nataliya Yu. Shitsev4; Gennady A. Komandin3; Andrey V. Muratov5; Yuri A. Aleshchenko5; Nickolay E. Sluchanko3
1Moscow Institute of Physics and Technology, Russian Federation; 2Moscow Institute of physics and technology, Russian Federation; 3Prokhorov General Physics Institute, Russian Academy of Sciences, Russian Federation; 4Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Ukraine; 5Lebedev Physical Institute, Russian Federation

First detailed measurements of terahertz-infrared electrodynamic response of high-quality single-crystalline Tm0.19Yb0.81B12 dodecaboride with dynamic charge stripes are performed at temperatures 5--300 K. Dramatic temperature changes in the dynamic conductivity spectra are observed, single-particle and collective excitations identified and their origin is discussed in terms of metal-insulator transition.

A Novel V-band Relativistic Transit-time Oscillator With High Power Handling Capacity

Bingfang Deng;
Juntao He; Junpu Ling; Xingjun Ge; Jinchuan Ju
College of Advanced Interdisciplinary Studies, National University of Defense Technology, China

A novel V-band coaxial transit-time oscillator (TTO) with high power handling capacity is presented. The interaction region is designed to operate in TM02 mode to increase power handling capacity of the device. By using a traveling wave output structure, the saturation time of the device is improved, and the maximum surface electric field is decreased. The output structure is also good for improving beam-wave interaction. To avoid mode competition, deep corrugation is applied to the slow wave structure, so the Rayleigh hypothesis is not satisfied. Hence the dispersion relation of the SWS in output structure is analyzed by mode matching method instead of Floquet harmonic expansion method. In numerical simulation, a 642MW microwave pulse at 60.0GHz is obtained with a diode voltage of 400kV and beam current of 5kA. The power conversion efficiency is about 32.1%.

Development Of A 140 GHz 50kW Gyrotron In IAE

Linlin Hu; Guowu Ma; Dimin Sun; Tingting Zhuo; Qili Huang; Hongbin Chen; Fanbao Meng
Institute of Applied Electronics, China Academy of Engineering Physics, China

A 140GHz 50kWgyrotron as the first development stage in IAE-CAEP has been fabricated and tested. In the experiment, the gyrotron has achieved a reliable CW operation at 20kW for 60s, long-pulse operation at 30kW for 20s and repetitive pulse operation at 50kW for 30s with 60% duty cycle. The extension of pulse duration was hindered by the outgassing of BN window due to overheating. The results further confirmed that BN window has limited power capacity for high-frequency high-power gyrotrons. A gyrotron with a CVD diamond window has been fabricated. The experiment will be carried out in the next half of 2019.

Powerful Relativistic Oscillators Of THz-band Based On Excitation Of Talbot-type Supermode In An Oversized Cavity

Andrey Savilov; Yulia Oparina;
Nikolai Peskov
Institute of Applied Physics RAS, Russian Federation

For relativistic oscillators, a new interaction regime is proposed based on the excitation of not a fixed transverse mode of the cavity, but a supermode formed by a fixed set of the transverse modes. Such regime is implemented in a quasi-optical cavity based on the Talbot effect, and allows to obtain narrow-band oscillation in a strongly oversized interaction space. Simulations of THz-band FEL with sub-GW to GW-level power driven by high-current relativistic electron beam are discussed

Investigation Of A Mini-Channel Cavity Cooling Concept For A 170 GHz, 2 MW Coaxial-Cavity Gyrotron

Stefan Illy; Konstantinos Avramidis; Philipp Bruecker; Gerd Gantenbein; Parth Kalaria; Sebastian Ruess; Manfred Thumm; John Jelonnek
Karlsruhe Institute of Technology / IHM, Germany

The maximum heat load on the cavity wall of high power fusion gyrotrons is one of the major limiting technological factors for the operation of the tube. To achieve the requested output power, efficiency and pulse length, a very efficient cooling of the interaction structure is mandatory. In this work, the performance of a mini-channel cavity cooling system for a 170 GHz, 2 MW coaxial-cavity gyrotron is numerically investigated, including the development of a mock-up test set-up for experimental validation.

Study On A Quasi-Optical Mode Converter For Gyrotron Based On Metamaterial

Wenjie Fu; Shijie Hu; Chaoyang Zhang; Xiaotong Guan; Yang Yan
University of Electronic Science and Technology of China, China

Artificial metamaterials offer unique functionalities for manipulating the spectral and spatial properties of electromagnetic waves in unconventional ways. In this paper, we report a transmission-type quasi-optical mode converter for gyrotron based on metamaterial. The initial simulation results show that the designed metamaterial quasi-optical mode converter is capable to transform the cylindrical TE01 mode to Gaussian beam, and the beam on the observed plane is with more than 95% scalar Gaussian mode content.


A Way To Match The Second Symmetric Mode Of Double-Grid Slow Wave Structure For Terahertz BWO

Yue Zhao1; Hairong Yin1; Jun Cheng1; Yanyu Wei1; Jin Xu1; Lingna Yue1; Jinjun Feng2
1University of Electronic Science and Technology of China, China; 2Beijing Vacuum Electronics Research Institute, China

In this paper, a way to match the second symmetric mode of double-grid slow wave structure designed for a practical 1-THz terahertz backward wave oscillator is presented. Simulation results show that the return loss is less than -15 dB, and the insertion loss is about -4 dB in the 50-GHz operating bandwidth.

Project Of Relativistic Mm-wave Amplifier With Multi-pass Interaction

Alexander Leontyev; Edward Abubakirov; Andrey Konyushkov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The concept of the amplifier based on double amplification of symmetrical and non-symmetrical modes in relativistic traveling wave tube (TWT) with modulating resonator is described. The input signal excites E01 mode which goes through the first pass of amplification. The hybrid HE11 mode is used for the second pass of amplification and output. The simplified model of amplifier is built and theoretical research of the amplifier operation in the Ka band was performed. It was shown that the double pass interaction can provide more than 40 dB of gain along with 30-35% operation efficiency.

Characteristics Of A Low-Voltage Gyrotron Backward-Wave Oscillator

Chien-Lun Hung1; Yi-Sheng Yeh2; Tsun-Hsu Chang3
1National Penghu University of Science and Technology, Taiwan; 2Southern Taiwan University of Science and Technology, Taiwan; 3National Tsing Hua University, Taiwan

Gyrotrons are usually operated on high voltages to generate high power coherent radiation in the millimeter to terahertz band. Recently, some high frequency applications do not require high power sources. For such applications, lowing the voltage of a gyrotron becomes an important issue. This study analyzes linear and nonlinear characteristics of a gyrotron backward-wave oscillator (gyro-BWO) operating in low voltage regime. Simulation results predict that the start-oscillation current of a gyro-BWO increases rapidly when the voltage decreases to a lower limit. Moreover, the efficiency and the tuning bandwidth of a low-voltage gyro-BWO are investigated.

Propagation Characteristics Of Periodic Azimuthally Corrugated Waveguides Derived By The FDTD Code COCHLEA

Dimitrios Peponis; Georgios Latsas; Ioannis Chelis;
Ioannis Tigelis
National and Kapodistrian University of Athens, Faculty of Physics, Greece

Azimuthal indentations have been proposed as an additional mean to suppress the parasitic oscillations in the gyrotron stacked beam-tunnel. As a first step, a smooth waveguide with azimuthal indentations was studied using COCHLEA code in order to identify their influence on the propagation characteristics. The S- parameters were calculated on the input and the output of the structure by decomposing the field into several modes. It was found that by increasing the indentations depth the field distributions change significantly and resonant effects are observed.

Design And Test Of 253/527 GHz Gyrotron for Spectroscopy Applications

Grigory Denisov1; Mikhail Morozkin1; Andrey Fokin1; Alexey Chirkov1; Andrey Kuftin1; Sergei Kornishin1; Evgeny Tai2; Anton Sedov1; Mikhail Proyavin1; Alexander Tsvetkov1; Mikhail Glyavin1
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; 2GYCOM Ltd, Russian Federation

A 527 GHz continuous-wave second harmonic gyrotron is in development at the IAP RAS jointly with GYCOM Ltd. as a microwave source for spectrometry and diagnostics of various media. We present first results of experimental measurements of this gyrotron including output power, power losses in the cavity, wave beam profile, frequency, and spectrum.

Out-of-Equilibrium Electrons And Record Thermionic Emission In LaB6

Elena Zhukova1; Boris Gorshunov1; Martin Dressel2; Gennady A. Komandin3; Mickhail Bednyakov1; Andrey V. Muratov4; Yuri A. Aleshchenko4; Mickhail Anisimov3; Nataliya Yu. Shitsevalova5; Anatoliy V. Dukhnenko5; Volodymyr B. Filipov5; Vladimir V. Voronov3; Nickolay E. Sluchanko3
1Moscow Institute of Physics and Technology, Russian Federation; 2Physikalisches Institut, Universität Stuttgart, Germany; 3Prokhorov General Physics Institute, Russian Academy of Sciences, Russian Federation; 4Lebedev Physical Institute, Russian Federation; 5Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Ukraine

To understand mechanisms of high thermionic emission of LaB6 we use infrared spectroscopy, DC resistivity and Hall-effect techniques to study conduction electrons state in LaB6 single crystals with different contents of 10B and 11B isotopes. We find that up to 70% of conduction electrons are strongly non-equilibrium due to involvement in the collective oscillations of electron density coupled to vibrations of Jahn-Teller unstable boron cage and rattling modes of La-ions. We claim that these non-equilibrium electrons determine the extraordinary low work function of thermoemission in LaB6.

Efficiency Enhancement Of High-Harmonic Gyrotron By Stable Excitation Of High Axial Mode In The TWT Regime

Ilya Bandurkin; Yury Kalynov; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The possibility of a stable excitation of a high axial mode in the traveling-wave tube regime in gyrotrons is demonstrated. Such an excitation becomes possible due to the use of a short element placed in the middle of the cavity and providing additional losses (either Ohmic losses or scattering into lower far-from-cutoff waves) for the near-to-cutoff first axial mode. This regime provides a significant efficiency enhancement in high-harmonic low-current gyrotrons.

Increasing The Diffraction Losses In Gyrotron Beam Tunnels For Improved Suppression Of Parasitic Oscillations

Ioannis Chelis1; Dimitrios Peponis2; Georgios Latsas2; Ioannis Tigelis2
1National and Kapodistrian University of Athens, Faculty of Physics, Greece; 2NKUA, Greece

High-power gyrotrons often suffer from parasitic oscillations in the compression region (beam tunnel) prior to the interaction cavity. A possible way to suppress the parasitic oscillations is to raise their starting currents by increasing the losses of the structure. In the present contribution we focus on the diffraction losses of the stacked copper-ceramic beam-tunnel concept. Parametric simulations show that the diffraction losses can be significantly increased by optimizing the geometric characteristics of the structure.

Wide Range Stepwise Frequency Tuning In Gyrotrons With Strong External Reflections

Irina Zotova1; Naum Ginzburg1; Andrey Malkin1; Roman Rozental1; Alexander Sergeev1; Mikhail Glyavin1; Seitaro Mitsudo2; Toshitaka Idehara2
1Institute of Applied Physics RAS, Russian Federation; 2Research Center for Development of Far-Infrared Region, University of Fukui, Japan

We demonstrate that in a gyrotron with strong external reflections, frequency jumping in a wide range is possible due to sequential excitation of axial modes in the gyro-TWT regime. Within the frame of a time-domain model, the frequency tuning in the range of 202.3-206 GHz and the output power of 0.5 kW is shown, when modes with a number of axial variations from 1 to 10 are excited. The obtained parameters are suitable for the positronium spectroscopy in a Fabry-Perot resonator.

Design Of A Quasi-optical Mode Converter For A Dual-frequency Coaxial-cavity Gyrotron

Jianbo Jin; Gerd Gantenbein; Tobias Ruess; Manfred Thumm; John Jelonnek
Karlsruhe Institute of Technology / IHM, Germany

A quasi-optical mode converter is under development for an 170/204 GHz coaxial-cavity gyrotron at KIT, which is operated in the TE34,19 mode at 170 GHz and the TE40,23 mode at 204 GHz. A mirror-line launcher should be used for such modes with the ratio of caustic to launcher radius to be approximately 0.32. The optimum value of the launcher radius has been found to provide RF beams with relative high Gaussian-mode contents for both operation modes.

Linear Analyses Of A 0.22 THz Confocal Waveguide Gyro-TWT

Jie Yang1; Shouxi Xu2; Yong Wang2
1University of Chinese Academy of Sciences, China; 2Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, China

Confocal waveguide gyrotron traveling wave tube (gyro-TWT) is a novel gyrotron amplifier which can operate in higher order modes and generate high power. In this paper, the linear theory derived from kinetic theory is presented to analyze a 0.22-THz confocal waveguide Gyro-TWT which operates at HE06 mode. The linear gain is 9.6 dB/cm at 220.2 GHz. Different parameters are pointed out to show their influences on critical current of absolute instability.

Theoretical Research On 300GHz Carbon Nanotube Cold Cathode Gyrotron

Lulu Shao1; Xuesong Yuan1; Weifeng Li1; Yu Zhang2; Bin Wang1; Hailong Li1; Yang Yan1
1University of Electronic Science and Technology of China, China; 2Sun Yat-Se University, China

A 300 GHz carbon nanotube cold cathode TE03 gyrotron has been studied in this paper. Carbon nanotube cold cathode gun is optimized. Simulation results show that the average output power of 148 W has been obtained. This gyrotron experiment will be performed based on these parameters in the future.

Using Reflections For Suppressing Parasitic Oscillation In A Multimode Gyrotron

Maria Melnikova1; Asel Adilova1; Nikita Ryskin2
1Saratov State University, Russian Federation; 2Saratov Branch, Institute of Radio Engineering and Electronics, RAS, Russian Federation

In recent years, the problem of control of gyrotron radiation by partial reflection of the output power from a remote load has attracted a considerable interest. In this paper, we study a reflection influence on mode-competition scenario in a multimode gyrotron. A possibility of controlling the mode competition processes by proper adjustment of reflection factors for different modes is discussed.


Simulations Of Sub-THz Confocal-Cavity Gyrotrons With Different Configurations Of Electron Beams

Mikhail Glyavin; Vladislav Zaslavski; Vladimir Manuilov; Irina Zotova; Dmitry Sobolev
Institute of Applied Physics Russian Academy of Sciences (IAP RAS), Russian Federation

Based on 3D PIC (particle-in-cell) simulations, we conduct a comparative analysis of operation of sub-THz confocal-cavity gyrotrons with two configurations of a driven electron beam namely, a conventional cylindrical hollow electron beam and a sheet rotating electron beam injected midway between the cavity mirrors. It is demonstrated, that for parameters of the experimentally realized 140 GHz confocal gyrotron, the starting and operating current can be significantly decreased with using the sheet rotating electron beam, while the efficiency of generation increases at least in 1.5 times (up to 30-35%). The smooth frequency tuning of 5% by mechanical variation of the distance between mirrors are also demonstrated.

Development Of 100 MW W-Band Gyrotron With Relativistic Sheet Electron Beam

Naum Ginzburg1; Andrey Malkin1; Roman Rozental1; Vladislav Zaslavsky1; Ilya Zheleznov1; Vladimir Tarakanov2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; 2Moscow Engineering Physics Institute, Russian Federation

Based on 3D PIC-simulations we study a possibility of development of a high-power W-band gyrotron driven by a sheet large-aperture relativistic electron beam. Improvement in selectivity can be provided by using a planar cavity, which is partially open over transverse (with respect to a beam motion) direction. It was demonstrated that for 500 keV/1 kA electron beam with the transverse size of ten wavelengths, a single-mode generation with 100 MW output power and efficiency of 20% can be obtained in the considered scheme.

Development Of Powerful W-band Planar Surface-Wave Oscillator Driven By High-Current Relativistic Sheet Electron Beam

Nikolai Peskov1; Andrey Arzhannikov2; Naum Ginzburg1; Petr Kalinin2; Tatiana Krapivnitskaya1; Eugene Sandalov2; Alexander Sergeev1; Stanislav Sinitsky2; Vasily Stepanov2; Vladislav Zaslavsky1
1Institute of Applied Physics RAS, Russian Federation; 2Budker Institute of Nuclear Physics RAS, Russian Federation

Project of powerful planar W-band surface-wave oscillator is under development in collaboration between IAP RAS (N.Novgorod) and BINP RAS (Novosibirsk) at the "ELMI" accelerator 1 MeV / 5 - 7 kA / 3 ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,µs. Electrodynamic system of this oscillator is based on a two-dimensional doubly-periodical structure, which combines properties of a slow-wave system that realizes conditions for an effective Cherenkov interaction with a high-current rectilinear sheet electron beam, and a high-Q resonator that implements mechanism of two-dimensional distributed feedback and provides selective excitation of the operating mode in the strongly oversized interaction space. Design parameters of the project are discussed and results of the simulations are presented, which demonstrate possibility to achieve in the considered scheme a stable narrow-band regime of oscillation with output power of the gigawatt level.

Spectral Radiation Pattern Of Bulk Waves Emitted By Thermally Stimulated Surface Plasmons At The Sample Edge

Ildus Khasanov1; Alexey Nikitin2; Vasily Gerasimov3
1Scientific and Technological Center of Unique Instrumentation of the Russian Academy of Sciences, Russian Federation; 2Scientific and Technological Center for Unique Instrumentation of RAS, Russian Federation; 3Budker Institute of Nuclear Physics SB RAS, Russian Federation

It was shown that the edge of a metal body face emits narrowly directed IR radiation with a spectrum of blackbody type, due to the surface plasmon nature of this radiation. Here we present the results of studies showing that the direction of the radiation pattern depends on its spectral composition. This confirms applicability of the analytical model for the diffraction field of monochromatic surface plasmon-polaritons (SPPs) to the case of broadband TSPPs.

High-Efficiency Gyrotron With Beam Energy Recovery

Oleg Louksha; Pavel Trofimov
Peter the Great St. Petersburg Polytechnic University, Russian Federation

This paper presents results of the combined 3-D simulation of a 74.2 GHz, 100 kW gyrotron with a four-stage depressed collector. The maximum overall efficiency of 72 % has been achieved as a result of improvement of electron beam quality and effective recovery of spent beam energy.

Compact Pulsed Magnets Designed For An 800 GHz, 2th Harmonics Gyrotron

Pengbo Wang1; Houxiu Xiao1; Donghui Xia2; Xin Qi1; Liang Li1; Xiaofeng Li1; Xianfei Chen1
1Huazhong University of Science and Technology, Wuhan National High Magnetic Field Center, China; 2Huazhong University of Science and Technology, School of Electrical and Electronics Engineering, China

This paper proposes the design of compact pulsed magnets for high frequency gyrotrons. With 12 layers of helices reinforced by zylon fibers, the pulsed magnet provides a magnetic field of 14.8 T for the 800 GHz gyrotron operating at the second harmonics. The pulse duration can be as much as 165 ms, and a pitch factor of 1.32 and a transverse velocity spread of 5.12% were obtained with the given electron gun geometry.

Design Of Quasi-Optical Mode Converter For 28GHz Gyrotron

Qili Huang; Dimin Sun; Linlin Hu; Tingting Zhuo; Guowu Ma; Hongbin Chen
Institute of Applied Electronics, China Academy of Engineering Physics, China

This paper presents the design of two quasi-optical mode converter for gyrotrons to transform the cavity waveguide mode TE02 and TE83 into a fundamental Gaussian beam. Those two quasi-optical mode converters are optimized by a combination of three methods, which are the scalar diffraction theorem, the K-S phase-correcting optimization iterative algorithm, and Geometrical Optics. According to the results, the conversion efficiency of energy is 92.5%( TE02) and 95%( TE83) and the Gaussian content of the output beam on the window surface is 99%.

Performance Tests Of ITER Gyrotrons And Design Study Of Dual-frequency ITER Gyrotron

Ryosuke Ikeda; Ken Kajiwara; Taku Nakai; Takayuki Kobayashi; Masayuki Terakado; Koji Takahashi; Keishi Sakamoto
National Institutes for Quantum and Radiological Science and Technology, Japan

Performance tests for two ITER gyrotrons have being carried out in the QST. In the tests, the output power of 1.05 MW with efficiency of 50.5 % for 300 s, the output power of 0.9 MW for 60 s in the 5 kHz full-modulation, and operation reliability of more than 90 % were achieved. Design study of dual-frequency gyrotron has been carried out to apply plasma operations at 1.8 T, 2.65 T and 5.3 T in ITER. It succeeded in design values of power transmission efficiencies in 104 GHz and 170 GHz oscillations almost equivalent to the design value in the current ITER gyrotron.

Double-Anode Sheet-Beam Electron Gun With A Circular Cathode For 220 GHz TWT
Shengkun Jiang1; Zhaoyun Duan1; Guang Yang1; Tao Tang1; Zhanliang Wang1; Huarong Gong1; Yubin Gong1; Ye Tang2; Pan Pan2; Jun Cai2; Jinjun Feng2
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; 2National Key Laboratory of Science and Technology on Vacuum Electronics in Beijing, Beijing Vacuum E, China

A 220 GHz double-anode sheet-beam electron gun with a circular cathode is designed using the three-dimensional particle simulation software Opera 18R2. The simulated results of beam current and the size of the beam waist are 140 mA and 0.5 mmÃfÆ'ââ,¬"0.1 mm at z=9 mm, respectively. This proposed double anode sheet beam electron gun is used in a T-shape staggered double-grating traveling wave tube (TWT).

TM-Mode Gyrotrons

Tsun-Hsu Chang
Department of Physics, National Tsing Hua University, Taiwan

Transverse magnetic (TM) waveguide modes have long been considered as the unsuitable modes for the operation of the electron cyclotron maser (ECM). This study reveals that certain TM modes might be suitable for gyrotrons --- ECM based devices. Unlike transverse electric (TE) modes, the linear behavior of the TM modes depends on the sign of the wave number kz. The negative kz has much stronger linear efficiency than that of the positive kz. In addition, the non-linear calculation for a fixed field profile shows that the efficiency of some TM modes could be as high as that of the TE modes. The current findings are encouraging and imply that TM modes might be advantageous to the gyrotron backward-wave oscillators.

Research On Y-Band Double Grating Diffraction Radiation Oscillators

Yaming Chen; Yaxin Zhang; Yilin Pan; Hexin Wang; Kaicheng Wang; Zhanliang Wang; Yubin Gong
University of Electronic Science and Technology of China, China

An open resonance systems (ORS) composed of cylindrical mirror and planar mirror was combined with double comb gratings, which was investigated in this paper. The results show that in such structure the electron beam will interacts with the quasi-optical mode in the cavity efficiently. The output power can reach to more than 3 W at 0.33 THz with about 2 GHz band width. This radiation system provides a potential way to develop high power and compact THz sources.

Study On The Beam-wave Interaction In A 28GHz Gyrotron With Complex Cavity

Yanwei Lu; Sheng Yu; Zhipeng Wang; Tianzhong Zhang; Rutai Chen; Wenjing Huang; Jin Luo
University of Electronic Science and Technology, China

In this paper, a 28GHz gyrotron with gradually tapered complex cavity is simulated and designed. In order to achieve high efficiency, we analyse the influences of the structural parameters on interaction efficiency, the effects of the electron beam parameters are also analyzed. The simulation results shows that the designed gyrotron can obtain output power of 43.18kW when the beam current is 2.1A, beam voltage is 53kV. The corresponding efficiency can reach to 38.80%.

Study On Hollow Cavity Of 140-GHz Gyrotrons

Yichi Zhang1; Bentian Liu2
1Beijing Vacuum Electronics Research Institute, China; 2National Key Laboratory of science and technology on Vacuum Electronics, China

To design an hollow cavity of 140-GHz Gyrotron, we conducted a study for TE22,6 mode cavity. Through changing magnetic field strength, voltage, current, radius and length of cavity, we analyzed the influence factors of structural parameters and electrical parameters on working performance. Under the experimental conditions of voltage 70kV and current 35A, we got a result which approximately the same with output power in fact.

Analysis On Resonator Coupling Characteristics Of Sub-THz EIA

Qinqin Yuan; Ziqiang Yang; Zongjun Shi; Ting Zhang; Xiaopin Tang; Feng Lan
Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology, China

The resonator coupling characteristics of Sub-THz extended interaction amplifier (EIA) with the grating and sub-wavelength hole array structure is simulated at the TM31-2π mode. Zero-field points of TM31-2π modes at the center of the beam tunnel promote an effective beam-wave interaction. The operating frequency of the intermediate cavity is 231.28 GHz with characteristic impedance of 207.74 Ω. The return losses of the input and output cavity are both better than 11.32 dB at 231.1 GHz, and the -3 dB bandwidth is 984 MHz.

Multiphonon Anharmonicity In MgO An Ionic Binary Compound

Paola Giura1; Lorenzo Paulatto2; Daniele Antonangeli2; Fei He2; Ricardo P. S. M. Lobo3; Eugenio Calandrini2; Alexei Bosak4; Luigi Paolasini4
1Sorbonne-University, France; 2IMPMC Sorbonne university, UMR CNRS 7590, France; 3ESPCI, LPEM, France; 4ESRF, France

The anharmonic lattice dynamics of MgO has been studied at ambient conditions and at high temperatures by infrared spectroscopy combined with density functional perturbation theory calculations. The agreement between the measured phonon energies and widths with ab-initio calculated values provides a direct and pertinent test of the validity of advanced theoretical methods. Long observed anharmonic features in the infrared reflectivity find a clear explanation in terms of well-defined multi-phonons scattering processes and lattice dynamics peculiarities, also responsible of a significant and sharp reduction of the longitudinal optical phonon lifetime at critical finite wave vectors. Our work highlights the importance of multi-phonons scattering processes on collective dynamics and related material properties

Pulsed Gyrotron Start-up Scenario In Presence Of Voltage/Current Surge Front

Yulia Novozhilova1; Nikita Ryskin2; Mikhail Glyavin1; et al1
1Institute of Applied Physics RAS, Russian Federation; 2Branch, Kotel'nikov Institute of Radio Engineering and Electronics RAS, Russian Federation

The possibility of high-efficiency single-mode regimes in a sub-megawatt power 250-GHz gyrotron, which is developed for the DEMO project, is studied. Nonlinear mode interaction at the front of accelerating voltage pulse/current is discussed. It is shown that for these scenarios a single-mode high-efficiency regime is possible within a fairly broad band of cyclotron frequency mismatch. Stability of such a regime with respect to the excitation of spurious modes is studied.

Powerful 1 THz Third-Harmonic Gyrotron For Plasma Applications

Yuriy Kalynov; Ilia Bandurkin; Vladimir Manuilov; Ivan Osharin; Andrey Savilov; Nikolai Zavolsky
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The possibility of creating a third-cyclotron-harmonic large-orbit gyrotron with a radiation frequency of 1 THz and an output power of several kilowatts for its use in promising plasma studies is studyed.


Competition Of Oscillations At Different High Cyclotron Harmonics In The Sub-THz Large-Orbit Gyrotron

Yuriy Kalynov; Ivan Osharin; Andrey Savilov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Recently, 30 keV/0.7A CW sub-THz large-orbit gyrotron have been experimentally realized. Two different modes at different (second and third) cyclotron harmonic were excited in the same cavity separately at slightly different magnetic fields. This work is dedicated to description of various regimes of competition of the two modes observed in the experiment.

1.0 THz BWO Based On Novel Helical Groove Rectangular Waveguide
Zhigang Lu; Ruidong Wen; Zhicheng Su; Weihua Ge; Tao Tang; Huarong Gong; Yubin Gong
University of Electronic Science and Technology of China, China

A novel helical groove rectangular waveguide slow wave structure (HGRW-SWS) is put forward to develop the lower operating voltage and high electron efficiency terahertz backward wave oscillator (BWO). The major advantage of the HGRW structure is its higher interaction impedance, lower ohm loss and lower operating voltage with respect to the typical SWSs such as folded waveguide SWS or double staggered grating SWS especially in the case of higher spatial harmonics. It is found that this kind of SWS can be operating on the n=-2 harmonic with the interaction impedance of more than 1.5 ohms from the analysis of the cold characteristics of the HGRW-SWS. Moreover, the beam-wave interaction results indicate that the BWO based on the HGRW SWS can produce the output power exceeding 0.657 W in the frequency range from 0.894 THz to 1.164 THz.

Two-dimensional Particle Simulation Analysis Of Ion Noise In TWT

Zhixin Yang; Zugen Guo; Rujing Ji; Zhigang Lu; Zhaoyun Duan; Yubin Gong; Huarong Gong
National Key Laboratory of Science and Technology on Vacuum Electronics, University of Electronic Science and Technology, China

In this paper, we establish a calculable TWT model to analyze the ion noise and adopt the intensity of fluctuation frequency and amplitude of ions and the average kinetic energy of electrons to indicate the strength of ion noise. The relationship between ion noise and the magnetic field is discussed. An effective way to suppress ion noise is adjustment of the magnetic field so that the interaction length is an integral multiple of the scalloping wavelength, decrease the accumulation of ions. The simulation results are consistent with the theoretical analysis.

Design Of Electron Optical System For 0.22THz Folded Waveguide TWT

Zugen Guo; Zhixin Yang; Rujing Ji; Ping Han; Lu Zhigang; Yubin Gong; Huarong Gong; Zhanliang Wang; Tao Tang
University of Electronic Science and Technology of China, School of Electronic Science and Engineering , China

An electron optical system(EOS) of 0.22THz folded waveguide travelling-wave tube (FW-TWT) was designed in this paper. The design process of Pierce gun and periodic permanent magnet focusing system was introduced in detail. The electromagnetic field simulation software Opera-3D was used to simulate and optimize the magnetic field. This simulation results show that the electron optical system transmitted beam current 33mA, cathode voltage -19kV, the first anode -3kV, and the beam transmission rate was 100%.


Analysis Of Folded Waveguide TWT With Non-Central Double Beams

Duo Xu1; Wei Shao1; Tenglong He1; Hexin Wang1; Zhanliang Wang1; Zhigang Lu1; Huarong Gong1; Zhaoyun Duan1; Jinjun Feng2; Yubin Gong1
1University of Electronic Science and Technology of China, China; 2Beijing Vacuum Electronics Research Insitute, China

In order to increase the output power of the folded waveguide (FW) Traveling wave tube (TWT), a novel Non-Central double beams (NCDB) FW-TWT is proposed in this paper. Compared with the traditional central beam (CB) FW-TWT, the NCDB-FW-TWT can double the output power without increasing the current of the single beam. A W-band NCDB-FW-TWT is designed in this paper. The PIC simulation results show that the maximal output power can reach 90 W and the 3-dB over 8.8%.

Cusp Electron Gun With Modulation Electrode For A THz Gyro-amplifier

Liang Zhang
1; Craig Donaldson2; Wenlong He3; Alan Phelps4; Adrian Cross1
1University of Strathclyde, United Kingdom; 2Department of Physics, University of Strathclyde, United Kingdom; 3Shenzhen University, College of Electronic Science and Technology, China; 4University of Strathclyde, Department of Physics, United Kingdom

A terahertz gyrotron traveling wave amplifier (gyro-TWA) centered at 370GHz is under development for the electron paramagnetic resonance (EPR) imaging application. This paper reports the investigation of a triode-type cusp electron gun for the terahertz gyro-TWA. The simulation results showed that at the beam alpha (the ratio of transverse to axial velocity) center of 1.07, an optimal alpha spread of ~10% was achieved, when it was operated at a beam voltage of 50 kV and a beam current of 0.35 A.

Possibilty of Super-Radiance At The Frequencies Of 3-5 THz From Short Electron Bunches Moving In Micro-Ondulators

Nezah Balal; Vladimir L. Bratman; Yuri Lurie
Ariel University, Israel

An available frequency range of coherent radiation from ps bunches with high charge can be significantly enhanced if one uses a micro-undulator with a high transverse field. Such an undulator with a helical symmetry can be implemented by redistributing a strong uniform magnetic field by a helical ferromagnetic insertion. Simulations demonstrate that using such undulators with period of 8-10 mm enable efficient coherent spontaneous radiation from short bunches with durations of (0.08-0.15) ps and super-radiance from extended bunches with duration of about 2 ps in frequency range of 3-5 THz.

Experimental Results Of Spectral And Imaging From Tunable Coherent Terahertz Radiation

Xuling Lin1; Jianbing Zhang2; Zhimin Dai2; Zhi Zhang1
1Beijing Institute of Space Mechanics and Electricity, China; 2Shanghai Institute of Applied Physics, Chinese Academy of Sciences, China

In this paper, we demonstrate the generation and observation of watt-level, coherent tunable terahertz radiation from relativistic femtosecond electron beam. Spectral content of the coherent terahertz emission from the undulator and dipole magnet is measured, and high quality terahertz imaging experimental is carried utilizing methodology of super-resolution reconstruction.


Studying Mechanical Properties And Phase Transitions Of Aspirin Polymorphs With Terahertz Spectroscopy And Ab Initio Simulations

Qi Li1; Andrew Bond2; Axel Zeitler1
1University of Cambridge, United Kingdom; 2University of Cambridge, Department of Chemistry, United Kingdom

Subtle structural differences and comparable lattice energies have triggered controversial discussions on the stabilities, mechanical properties and further comparisons between two polymorphs of aspirin. In this study, terahertz time-domain spectroscopy (THz-TDS) is coupled with density functional theory (DFT) and ab initio molecule dynamics (AIMD) calculations to seek physical insight into the properties of crystalline aspirin. Large-size supercells incorporating defects are used to simulate disorder in the aspirin crystal structure to investigate possible mechanisms for polymorphic transformation. THz-TDS of aspirin single crystals is performed to investigate certain interesting modes that may play a critical role in the phase transitions and mechanical properties of aspirin.

Anisotropic MagnetoResistance Of 3d Ferromagnetic Metals Observed by THz-TDS
JiHo Park1; Soo gil Lee1; Jeong Mok Kim2; Nyun Jong Lee3; Sanghoon Kim3; Byong Guk Park2; Kab Jin Kim1
1Department of Physics, KAIST, Republic of Korea; 2Department of Materials Science and Engineering, KAIST, Republic of Korea; 3Department of Physics, University Of Ulsan, Republic of Korea

Electrical resistance of magnetic materials depends on magnetization orientation of the sample. The representative example is anisotropic magnetoresistance (AMR)[1]. Despite a number of experimental reports, our understanding on the microscopic origin of AMR is still far from complete. Theory has predicted that the AMR originates from different electronic scattering from conduction s,p and d bands to localized d band [2] which is closely related to spin orbit coupling (SOC). However, the microscopic mechanism underlying the scattering process is yet to be fully understood experimentally. Therefore, a direct measurement of electron scattering is important for revealing the origin of AMR. Using THz-TDS, here we directly access the scattering time of conduction electron in 3d metallic ferromagnets.

Tilted-Pulse-Front Pumped Plane-Parallel LiNbO3 Slab THz Source

Priyo Nugraha; Gergo Krizsan; Csaba Lombosi; Laszlo Palfalvi; Gyorgy Toth; Gabor Almasi; Janos Hebling; Jozsef Fulop
Institute of Physics, University of Pecs, Hungary

A new type of tilted-pulse-front pumped terahertz (THz) source has been demonstrated, which is based on a LiNbO3 plane-parallel slab with an echelon structure on its input surface. The use of a plane-parallel nonlinear optical crystal slab enables straightforward scaling to high THz pulse energies and the production of a symmetric THz beam with a uniform pulse shape for good focusability and high field strength.

Terahertz Plasmonic Photocurrents In Graphene Nanostructures

Viacheslav Popov; Denis Fateev
Kotelnikov Institute of Radio Engineering and Electronics, Russian Federation

The theory of plasmon detection of terahertz radiation in a periodic graphene structure with spatially inhomogeneous graphene near the Dirac point is developed.


Development Of The Second Harmonic 190 GHz Gyrotron For OAM Communication

Ashwini Sawant; Ingeun Lee; Mun Seok Choe; EunMi Choi
Ulsan National Institute of Science and Technology (UNIST), Republic of Korea

We presented the design of a 190 GHz second harmonic gyrotron capable of generating few kWs of power in a mode-pair TE8,3 and TE11,2 at 33 and 37 kV voltage respectively. Conventional cavity with two sinusoidal perturbations has been used to reduce the mode competition from fundamental mode. It is designed for the conceptual study of OAM communication using gyrotron mode.

Design And Fabrication Of A D-Band Traveling Wave Tube For Millimeter Wave Communications

Rupa Basu; Laxma Billa; Jeevan Rao; Rosa Letizia; Claudio Paoloni
Lancaster University, United Kingdom

The design and fabrication aspects of a novel D-band (141 GHz-148.5 GHz) Traveling Wave Tube (TWT) for enabling the first point to multipoint front end at D-band, objective of European Commission H2020 ULTRAWAVE is presented. The ULTRAWAVE system will provide unprecedented wireless area capacity over wide area sectors, with radius up to 500 - 600 m for the future 5G high density small cell deployment. The design and fabrication processes adopted for the TWT are focused to find new low cost solutions for TWTs at millimetre waves to satisfy the requirements of the wireless market. The proposed TWT will provide more than 10 W saturated output power for achieving more than 100 Gb/s/km2 of area capacity over 600 meters radius wide angle sector, with 99.99% availability in ITU zone K.

Development Of High-Harmonic CW Gyrotron With An Operating Frequency Of 1.2 THz

Alexander Tsvetkov
1; Vladimir Manuilov1; Irina Zotova1; Ilya Bandurkin1; Alexey Fedotov1; Vladislav Zaslavsky1; Yoshinori Tatematsu2; Seitaro Mitsudo2; Toshitaka Idehara2; Mikhail Glyavin1
1Institute of Applied Physics RAS, Russian Federation; 2Research Center for Development of Far-Infrared Region, University of Fukui, Japan

The report is devoted to development of a 3d harmonic CW gyrotron with the record output frequency of 1.2 THz. Based on analyses of start currents we demonstrate, that improvement of mode selectivity can be achieved due to interaction with an electron beam having a specially increased (up to 30-40%) velocity spread. In such conditions the start current of a near-cutoff operating mode decreases due to influence of "slow" electron fractions in the electron beams. At the same time, the start currents of parasitic modes, which are very sensitive to the velocity spread, increases significantly. The suppression of spurious mode and selective excitation an operating TE15,6 mode is demonstrated in the frame of 3D particle-in-cell simulations using CST STUDIO SUITE.

The Effect Of The Lossy Material On The Modes In A Smooth Metallic Dielectric Loaded Gyrotron Beam Tunnel

George Latsas1; Ioannis Tigelis1; Jeremy Genoud2; Stefano Alberti2
1National and Kapodistrian University of Athens/ Faculty of Physics, Greece; 2École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, Switzerland

The effect of the dielectric material on the dispersion properties and behavior of the modes in a smooth metallic gyrotron beam tunnel, partially filled with a lossy dielectric material, is studied. Two kinds of modes were identified, one located inside the empty region and the other inside the dielectric region. It was seen that these two kinds of modes are not equally affected by the changes in the geometry and dielectric characteristics.

Design Of An 800GHz Gyrotron

Xianfei Chen; Houxiu Xiao; Tao Peng; Donghui Xia; Xin Qi; Pengbo Wang
Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, China

The design of an 800GHz gyrotron with output power of 172kW is presented. This gyrotron operates at fundamental resonance with a 30T pulsed magnet. The parameters are optimized according to the normalized parameters. The simulation results show that the maximum efficiency of 43% can be reached.

Experimental Study Of The Emission Properties Of Magnetron Injection Guns For High-Power Gyrotrons

Zisis Ioannidis; Tomasz Rzesnicki; Ioannis Pagonakis; Gerd Gantenbein; John Jelonnek
Karlsruhe Institute of Technology, Germany

The quality of the electron beam generated by a magnetron injection gun (MIG) is very important in order to ensure the excellent performance of high-frequency, high-power gyrotrons. A diagnostic device, operating at scaled down parameters, was recently developed at KIT in order to study the emission properties of various MIGs that are used with prototype modular short-pulse gyrotrons. Herein, we present the first experimental results that were obtained for electron guns that are used with coaxial 2 MW, 170 GHz gyrotrons.

Electrically-controlled THz Emission From AlGaN/GaN/Al2O3 High Electron Mobility Transistor Structures At A Temperature Of 20 K

Ignas Grigelionis1; Pawel Prystawko2; Irmantas Kasalynas1
1Center for Physical Sciences and Technology, Lithuania; 2Institute of High Pressure Physics UNIPRESS, Poland

We investigated radiative phenomena contributing to the THz emission of AlGaN/GaN high electron mobility transistor (HEMT) structures grown on sapphire substrate. Electrically controlled emission spectroscopy was performed in the frequency range 100-600 cm-1 at a temperature of 20 K. The electroluminescence from nitrogen vacancies in GaN buffer layer contributed to the THz emission spectrum, and the amplitude and frequency of the observed narrow emission lines were controlled by applied voltage.

Electric Dipole-free Meta-cylinders

Mahdi Safari1; Ali Momeni2; Ali Abdolali2; Nazir P. Kherani1
1Department of Electrical and Computer Engineering, University of Toronto, Canada; 2Department of Electrical Engineering, Iran University of Science and Technology, Iran

In this paper, we propose a novel asymmetrical meta-atom for control of electromagnetic wave based on analytical formulation. Here, we show that the proposed meta-cylinder is flexible and well capable of achieving exotic electromagnetic responses.



Tuesday 3 September 2019


09:00-10:30 - Plenary Sessions - Amphi Lavoisier

Chairperson: Jean-Louis Coutaz

09:00 Tu-Pl-1

TeraHertz Josephson Plasmonics: Controlling Supercurents in Cuprates

Andrea CAVALLERI, Max Plank Institute, Structure and Dynamics of Matter, Germany

09:45 Tu-Pl-2

Building Blocks And Concepts For THz Remote Sensing And Communications

Daniel DOLFI, Thales Research & Technology, France

10:30-11:00 - Coffee Break

11:00-12:30 Parallel sessions Tu-AM

11:00-12:30 - Tu-AM-1 - Gyrotron 4 - Amphi Lavoisier

Chairperson: Manfred Thumm

11:00 Tu-AM-1-1
Gyro-TWTs With Helically Corrugated Waveguides: Overview Of The Main Principles
Grigory Denisov; Alexander Bogdashov; Igor Gachev; Sergei Samsonov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

An overview of the main principles of operation and design for major components of the gyrotron travelling-wave tube (gyro-TWT) based on a helically corrugated waveguide is presented

11:30 Tu-AM-1-2
Recent Progress In K-band Technological Gyrotrons Development
Mikhail Glyavin1; Mikhail Proyavin1; Vladimir Manuilov2; et al1
1Institute of Applied Physics RAS, Russian Federation; 2NNSU, Russian Federation

The overview of recent results and trends of the development of K-band (24-30 GHz) technological gyrotrons are given. The high-efficient second harmonic CW gyrotrons with output power up to 15 kW has been developed and tested. It is shown that promising technologies needs power increasing up to several tens kW. Due to the problem of suppression of high harmonics by fundamental one, the project of powerful CW first harmonic gyrotron is proposed. The reduction of total power consumption is realized by the magnetic system shielded by ferromagnetic screens. The report presented the 28 GHz CW technological gyrotron with the output power 25-30 kW and total (including the power consumption of the main coil) efficiency 35%. The characteristic features of the magnet, electron beam optics and electrodynamics system are described.

11:45 Tu-AM-1-3
Frequency-Tunable Reflective Gyro-BWO
Cheng-Hung Tsai
1; Tsun-Hsu Chang1; Yoshinori Tatematsu2
1Department of Physics, National Tsing Hua University, Taiwan; 2Research Center for Development of Far-Infrared Region, University of Fukui, Japan

We design and fabricate a novel electron gun and conduct an experiment using a tapered structure for the reflective gyrotron backward-wave oscillator (gyro-BWO). The electron gun and the interaction structure provide an ideal beam-wave coupling which enhances the interaction efficiency over a broad bandwidth. The cutoff section and mild tapers in the cavity region help to generate the 203 GHz waves operating at TE02 mode with the peak power efficiency of 30% and a wide bandwidth of 8.5 GHz. Preliminary experimental results will be reported.

12:00 Tu-AM-1-4
Broadband Terahertz Frequency Comb Generation From Guided Mode Resonance Excited By Fast Electrons

Tao Zhao; Min Hu; Renbin Zhong; Diwei Liu; Zhunhua Wu; Sen Gong; Shenggang Liu
University of Electric Science and Technolgy of China, China

A physical mechanism of generating tunable terahertz (THz) frequency combs (FCs) with ultra-broad bandwidth of >4 THz and high repetition rate above 20 GHz is presented. An analytical model and diffraction theory demonstrate that the equidistant comb modes are generated from the resonance between the modes of a dielectric waveguide and diffraction waves from a grating adjacent to the waveguide excited by fast electrons. Furthermore, a frequency metrology of the THz FC is developed, and demonstrated to be capable of performing high-precision measurements. This mechanism provides a new way to generate THz FCs with broad bandwidth and large frequency spacing.

12:15 Tu-AM-1-5
Recent Development For THz Vacuum Electronic Devices In IAE

Hongbin Chen;
Wenqiang Lei; Guowu Ma; Peng Hu; Yi Jiang; Linlin Hu; Dimin Sun; Yinhu Huang
Institute of Applied Electronics, China Academy of Engineer Physics, China

Institute of Applied Electronics (IAE) of China Academy of Engineer Physics (CAEP) has been developing Grotron and traveling wave tubes operating in the terahertz wave regimes, such as 0.14THz, 0.22THz, 0.34THz. The 0.22THz and 0.34THz pulse folded waveguide TWTs and the CW 0.14THz and 0.22THz folded waveguide TWTs have been measured. By the measurement of 0.22THz pulse TWT, the output power is about 18.2W in 216GHz and 217GHz, the maximum gain is 28.2dB. -3dB bandwidth is about 10GHz at 50% duty cycle. In 0.34THz pulse folded waveguide TWT, the output power is about 1.61W in 338.24GHz, the maximum gain is 23.63dB. -3dB bandwidth is about 1.4GHz at 30% duty cycle. 0.14THz Gyrotron oscillator has been developed and measured at long time pulse work. The output power is about 30kW worked at 60s. 0.67THz and 1THz folded waveguide TWTs is being designed in IAE in this year.

11:00 - 12:30 Tu-AM-2 Supercond. Devices

Chairperson: Masayoshi Tonouchi Petit Amphi

11:00 Tu-AM-2-1
Development Of High-Tc Superconducting THz Emitters
Takanari Kashiwagi1; Shungo Nakagawa1; Takayuki Imai1; Genki Kuwano1; Youta Kaneko1; Yukino Ono1; Shinji Kusunose1; Takashi Yamamoto2; Hidetoshi Minami1; Manabu Tsujimoto1; Kazuo Kadowaki3
1University of Tsukuba, Japan; 2QuTech, Delft University of Technology, Netherlands; 3Algae Biomass and Energy System R & D Center, University of Tsukuba, Japan

Since the discovery of continuous, coherent THz radiation from intrinsic Josephson junctions (IJJs) constructed in the single crystals of Bi2Sr2CaCu2O8+δ in 2007, various types of device structures have been developed. Thermal management of Joule heat in the IJJ mesa structure is the most important point for the improvement of the radiation characteristics of the IJJ-THz emitters. The radiation frequencies ranging from 0.3 to 2.4 THz, the emission power of ~30 μW and the radiation linewidth of 0.2 GHz at ~0.5 THz were obtained from the thermal managed device structures so far. These characteristics will be discussed in the conference.

11:30 Tu-AM-2-2
Semiconducting Y-Ba-Cu-O Thin Film Detectors At Room Temperature: Front End And Back End Design Issues From Near To Far Infrared

Annick Degardin1; Vishal Jagtap2; David Alamarguy3; Xavier Galiano2; Alain Kreisler1
1Sorbonne-University, GeePs, France; 2CentraleSupelec/GeePs, France; 3CNRS/GeePs, France

The Y-Ba-CuO semiconductor material, particularly in its amorphous form (a-YBCO), offers an attractive solution for the easy production of thermal radiation detectors operating at room temperature, because it exhibits a sensitive pyroelectric response. Two aspects must be foreseen, however, for an optimized design of such detectors, in terms of sensitivity and noise level. The front end aspect is related to the optical and thermal coupling of an a-YBCO thin film with the incident radiation. It involves the absorption coefficient, which strongly decreases as wavelength increases. The backend aspect is related to the electrical match between the sensing film and the readout circuitry. It involves the ohmic or Schottky nature of the metal/a-YBCO contacts. We conclude with some design examples and performances, for both planar and trilayer devices. In the near-infrared for instance, noise equivalent power values below 15 pW/√Hz, and detectivity values above 10^9 cm.√Hz/W, could be measured.

11:45 Tu-AM-2-3
Towards Classical Josephson Terahertz Detector

Yuriy Divin; Irina Gundareva; Valery Pavlovskiy
Kotelnikov Institute of Radio Engineering and Electronics, Russian Federation

High-Tc Josephson junctions with Josephson dynamics suppressed by thermal fluctuations were evaluated as detectors of electromagnetic radiation. Classical rectification of THz radiation in the frequency range below 1 THz and in the power range of 4 decades in YBa2Cu3O7-x bicrystal Josephson junctions was experimentally found. As the result of analytical and numerical calculations, the NEP-value of 7x10^(-15) W/Hz^(1/2) and power dynamic range of 3x10^5 at the frequencies up to 1.4 THz were obtained for quasiclassical detection with YBa2Cu3O7-x Josephson junctions operating at the temperature T of 50 K.

12:00 Tu-AM-2-4
Detailed Design Of NbN Based Kinetic Inductance Detectors For Polarimetric Diagnostics

Francesco Mazzocchi1; Eduard Driessen2; Shibo Shu2; Theo Scherer1; Dirk Strauss1
1Karlsruhe Institute Of Technology, Germany; 2IRAM, France

In the following work, we present the detailed design of a polarization sensitive, NbN base Kinetic Inductance Detector to be employed in a low cost, small footprint polarimeter for fusion plasma diagnostics.

12:15 Tu-AM-2-5
Monolithic Terahertz Emitter Of High-temperature Superconductors

Itsuhiro Kakeya1; Asem Elarabi1; Keiichiro Maeda1; Shuma Fujita1; Manabu Tsujimoto2
1Kyoto University, Japan; 2University of Tsukuba, Japan

Emission of terahertz electromagnetic (EM) waves from a high critical temperature (Tc) superconductor intrinsic Josephson junction (IJJ) is a new and promising candidate for practical applications of superconducting devices. The emitted EM waves are considered to be coherent because the emission is yielded by synchronization of thousand stacked IJJs consisting of the mesa device. The device has advantages of broad range of frequency tuning and manipulation of polarization with monolithic device structure.

11:00 - 12:30 Tu-AM-3 High Fields 2

Chairperson: Alexander Shkurinov Room 162

11:00 Tu-AM-3-1

Generation Of MV/cm Longitudinal Terahertz Electric Fields From Relativistic Laser-solid Interactions
Abel Hailu Woldegeorgis1; Takayuki Kurihara2; Mohammed Almassarani1; Amrutha Gopal1
1Helmholtz Institute Jena, Helmholtz Institute Jena, Fröbelstieg 3, Germany; 2University of Konstanz, University of Konstanz, Universitatsstr. 10, Germany

We report on the generation and detection of longitudinal terahertz (THz) transient, with field strength of 1.5 MV/cm, at the focus of a radially polarized high-power terahertz beam generated at the rear surface of a thin metal foil irradiated by multi-terawatt laser pulse. An f/1.5 off-axis parabolic mirror was used to focus the collimated THz beam. In addition to the longitudinal field, a transverse field, albeit off-axis, with amplitude in excess of 3 MV/cm was also measured.

11:30 Tu-AM-3-2
Energy Spread And Emittance Control In Segmented High Field Terahertz Driven Electron Accelerators

Dongfang Zhang; Arya Fallahi; Michael Hemmer; Hong Ye; Moein Fakhari; Yi Hua; Huseyin Cankaya; Anne-Laure Calendron; Luis E. Zapata; Nicholas H. Matlis; Franz X. Kärtner
Deutsches Elektronen-Synchrotron (DESY), Germany

Here we use a two-stage segmented-terahertz-electron-accelerator-and-manipulator (STEAM) setup to demonstrate control over the electron beam energy, energy spread and emittance. The first rebunching stage is used to tune the duration of 55 keV electron bunches that enables femtosecond phase control at the second accelerating stage. For optimized parameters, energy spread and emittance are reduced by 4x and 6x, respectively, relative to operation with the first stage off. A record energy gain of ~70 keV was achieved at a peak accelerating field of 200 MV/m, resulting in >100% energy boost in a THz-powered accelerator for the first time.

11:45 Tu-AM-3-3
High Harmonic Generation In Metallic Phase Of 2H-NbSe_2
Kousei Shimomua; Kento Uchida; Kohei Nagai; Satoshi Kusaba; Koichiro Tanaka
Department of Physics, Graduate School of Science, Kyoto University, Japan

High harmonics up to the 9th order have been confirmed in metallic phase of 2H-NbSe2 with intense mid-infrared light. They show the nonperturvative excitation power dependence, and their efficiency are almost independent of the polarization direction to the crystal axis. Our Numerical calculation based on the intraband current model reproduces the experimental results, suggesting that the carrier distribution in k-space plays a crucial role for the high harmonics in metal.

12:00 Tu-AM-3-4
Terahertz Generation By Kerr Effect At Metal Surfaces

Bastien Muller; Maxime Bernier; Emilie Herault; Jean-Louis Coutaz

The emission of terahertz radiation from laser-excited thick metal samples through Kerr effect has been detected for the first time to the authors' knowledge. The observed THz waveforms are generated through nonlinear electronic processes at surfaces (optical rectification) and in the bulk (Kerr effect) of gold samples.

12:15 Tu-AM-3-5

Extremely High Field Single-cycle Terahertz Pulse Sources Based On Echelon Structures
György Tóth1; László Pálfalvi1; József András Fülöp2; Gergő Krizsán1; Priyo S. Nugraha3; Zoltán Tibai1; Levente Tokodi1; Gábor Almási1; János Hebling1
1University of Pécs, Hungary; 2MTA-PTE High Field Research Group, Hungary; 3Szentágothai Research Centre, Hungary

Three different echelon based structures for the generation of intense THz pulses were suggested and simulated. Their advantages are the energy scalability and the symmetric THz beam profile. Focused single cycle THz pulses up to ~50 MV/cm peak electric field level are predicted with these sources. Such sources can basically promote the realization of THz driven electron and proton accelerators.

11:00 - 12:30 Tu-AM-4 Telecom 1

Chairperson: Tadao Nagatsuma Room 269

11:00 Tu-AM-4-1

Simulation And Automatic Planning Of 300 GHz Backhaul Links
Bo Kum Jung; Nils Dreyer; Johannes Eckhardt; Thomas Kürner
TU Braunschweig, Germany

The IEEE Standard 802.15.3d defines a communication systems allowing wireless solutions for backhaul links operating at 300 GHz with data rates of 100 Gbit/s and beyond. The European Horizon 2020 ThoR project works towards the demonstration of such a solution. One of the goals of ThoR is to develop algorithms for automatic planning of 300 GHz backhaul links and the derivation of planning guidelines. In this paper, an automatic algorithm for the planning of 300 GHz backhaul links using 3D ray tracing taking into account atmospheric effects is presented. The influence of both the applied antennas and the weather conditions are evaluated for an automatically planned network by using a realistic scenario of an ultra-dense network in the city of Hannover.

11:30 Tu-AM-4-2
Bidirectional K-Band Photonic/Wireless Link For 5G Communications
Alvaro Morales; Dimitrios Konstantinou; Simon Rommel; Thiago Roberto Raddo; Ulf Johannsen; Chigo Okonkwo; Idelfonso Tafur Monroy
Eindhoven University of Technology, Netherlands

A bidirectional analogue radio-over-fiber link based on photonic heterodyning and time-division duplex is experimentally demonstrated, successfully transmitting 5G OFDM signals with data rates of 2.4 Gbit/s and 1.2 Gbit/s in down- and uplink directions over 4 m of wireless distance.

11:45 Tu-AM-4-3
Scattering Analysis Of Terahertz Wireless Links By Rough Surfaces
Jianjun Ma
1; Rabi Shrestha2; Wei Zhang2; Lothar Moeller3; Daniel Mittleman2
1Beijing Institute of Technology, China; 2Brown University, United States; 3New Jersey Institute of Technology, United States

This work presents the diffuse bistatic scattering response of metallic rough surfaces using a data stream at THz frequency range. NLOS links can be established by the form of diffuse scattering rays when a LOS and specular NLOS links are blocked. So non-specular NLOS paths can play a valuable role in future THz wireless systems with a highly directional beam.

12:00 Tu-AM-4-4
Direct Terahertz Communications With Wireless And Fiber Links

Xiongbin Yu1; Tomoyuki Miyamoto2; Katsunori Obata2; Yasuo Hosoda2; Jae-Young Kim3; Masayuki Fujita1; Tadao Nagatsuma1
1Osaka University, Japan; 2Pioneer Corporation, Japan; 3ROHM Co., Ltd, Japan

We have successfully demonstrated a direct THz communications link that employs both a wireless and a fiber portion, for advanced communication systems. Currently, the greatest obstacle is the efficiency of overall link, which we intend to overcome by refining the connection between the photonic-crystal waveguide and THz fiber, in order to achieve a higher data rate. We also aim to employ RTDs as both transmitter and receiver, in order to realize an all-electronic system that does not require laser excitation. Such THz systems may find uses not only in communications, but also in such as remoting sensing, security and medical applications.

12:15 Tu-AM-4-5
Towards Super-heterodyne THz Links Pumped By Photonic Local Oscillators

Iulia Dan
1; Shintaro Hisatake2; Pascal Szriftgiser3; Ralf-Peter Braun4; Ingmar Kalfass1; Guillaume Ducournau5
1Institute of Robust Power Semiconductor Systems, Univ Stuttgart, Germany; 2Gifu Univ, Japan; 3PhLAM, France; 4DEUTSCHE TELEKOM AG, Germany; 5IEMN CNRS/Université de Lille, France

We present in this paper wireless data transmission experiments in a superheterodyne wireless system based on millimeterwave monolithic integrated circuits at a center frequency of 300 GHz, driven by photonic local oscillator (LO). Superheterodyne operation is attractive for compliance with the recent IEEE802.15.3d frequency standard. The super-heterodyne transmission with two channels is realized using an AWG and a photonic-based LO. The paper presents initial transmission experiments realized using two channels in the 300 GHz band

11:00 - 12:30 Tu-AM-5 QW

Chairperson: Yanko Todorov Room 101

11:00 Tu-AM-5-1

Quantum Well Infrared Detectors In The Strong Light-matter Coupling Regime
PB Vigneron
1; S Pirotta1; I Carusotto2; NL Tran1; G Biasiol3; JM Manceau4; A Bousseksou4; Raffaele Colombelli4
1Centre de Nanosciences et Nanotechnologies (C2N), France; 2University of TRENTO, BEC Center, Italy; 3TASC Laboratory, Italy; 4Centre de Nanosciences et Nanotechnologies, France

We report quantum well mid-infrared photo-detectors operating in the strong light-matter coupling regime. It is an ideal system to elucidate the elusive problem of the injection of electrons (single-particles) into polaritonic modes (bosonic excitations). We have obtained experimental information on the transfer function between a polaritonic system and an electronic reservoir. This approach opens promising avenues in view of adding previously unavailable functionalities to quantum well detectors and improving their performance.

11:30 Tu-AM-5-2
High Speed Quantum Well Infrared Heterodyne Receivers At 4.9µm
Gregoire Vallet1; Djamal Gacemi1; Azzurra Bigioli1; Angela Vasanelli1; Yanko Todorov1; Carlo Sirtori1; Etienne Rodriguez2
1Laboratoire de Physique de l'Ecole Normale Superieure, CNRS, France; 2CINTRA CNRS/NTU/THALES, Singapore

We have realized high-speed quantum well infrared photodetectors (QWIPs) for the detection of coherent radiation at 4.9 Ãfâ?sÃ,µm wavelength. Our devices have a detectivity of 4 x 10-10 cm Hz1/2 W-1 at 77 K and a flat response up to 30 GHz.

11:45 Tu-AM-5-3
Far And Mid IR Stimulated Emission In HgCdTe QW Heterostructures

Vladimir Gavrilenko1; Sergey Morozov1; Vladimir Rumyantsev1; Mikhail Fadeev1; Vladimir Utochkin1; Nikita Kulikov1; Alexandre Dubinov1; Vladimir Aleshkin1; Nikolay Mikhailov2; Sergey Dvoretskii2; Frederic Teppe3; Carlo Sirtori4
1Institute for Physics of Microstructures, Russian Federation; 2A.V.Rzhanov Institute of Semiconductor Physics, Russian Federation; 3Laboratoire Charles Coulomb, CNRS & Universite Montpellier, France; 4Laboratoire de Physique de l'Ecole Normale Superieure, France

Stimulated emission (SE) at wavelengths up to 24 μm (12.5 THz) and down to 2.8 μm is demonstrated from HgCdTe quantum well (QW) heterostructures. Non-radiative Auger recombination is show to be mitigated due to relativistic energy spectrum. Pump-probe carrier lifetime measurements show that further increase in SE wavelength is feasible up to 60 μm (5 THz). In the short wavelength range SE down to 2.8 μm is demonstrated at temperatures available with Peltier coolers.

12:00 Tu-AM-5-4
Room Temperature THz Intersubband Transitions In Continuously-graded AlxGa1-xAs Parabolic Quantum Wells

Christopher Deimert1; Paul Goulain2; Jean-Michel Manceau2; Adel Bousseksou2; Raffaele Colombelli2; Zbig Wasilewski1
1University of Waterloo, Canada; 2centre de nanosciences et naotechnologies, France

We demonstrate room temperature intersubband transitions in the THz range using continuously-graded AlxGa1 xAs parabolic quantum wells. Below 100K, the linewidth of the transition reaches a record-low value of 5.7% of the central frequency.

12:15 Tu-AM-5-5
High Sensitivity 9?m Metamaterial Infrared QC Detectors At 300K

Azzurra Bigioli1; Giovanni Armaroli1; Daniele Palaferri2; Yanko Todorov1; Angela Vasanelli1; Djamal Gacemi1; Li Lianhe3; Giles Davies3; Edmund Linfield3; Carlo Sirtori1
1Laboratoire de Physique de l'Ecole Normale Superieure, France; 2Laboratoire Matériaux et Phénomènes Quantiques, France; 3School of Electronic and Electrical Engineering, Leeds, United Kingdom

Quantum Cascade Detectors are promising devices for high-temperature mid-infrared detection. The responsivity, related to its photovoltaic working principle, still suffers from lower responsivity respect to a photoconductive device such as QWIP. Here, we demonstrate that inserting a QCD detector in a photonic metamaterial made of patch-antenna microcavities, we can boost light-matter interaction reaching responsivity value in the order of 50mA/W at room temperature, the highest value reported in the literature

11:00 - 12:30 Tu-AM-6 Metamaterials 1

Chairperson: Michele Ortolani Room 151

11:00 Tu-AM-6-1

Broadband Achromatic Metalens In Terahertz Regime
Yiming Zhu; Qingqing Cheng; Lin Chen; Yan Peng
University of Shanghai for Science & Technology, China

We demonstrate the achromatic metalens with C-shape units working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the center wavelength. The achromatic focusing has been observed both experimentally and numerically, with the size of focal spot closed to ?. Meanwhile, the designed metalens possesses high working efficiency of more than 68% at the peak and a relatively high numerical aperture (NA) of NA=0.385 in order to obtain high spatial resolution. We further show the robustness of our C-shape structures, considering lateral shape deformations and deviations of etching depth. Our work successfully demonstrates the THz achromatic metalens, which opens an avenue for the future applications of terahertz meta-devices on spectroscopy, time-of-flight tomography and hyperspectral imaging system.

11:30 Tu-AM-6-2
Terahertz 3D Components Made From Metamaterials

Haruaki Nakao; Takehito Suzuki
Tokyo University of Agriculture and Technology, Japan

A realization of next-generation ultrafast wireless communication (6G) and security imaging in the terahertz waveband is a question of time because of the rapid development of terahertz oscillators. However, terahertz components have yet to be developed whereas components in the optical region and millimeter waveband provide sufficient support for technological and scientific progress. Here we produce a reflectionless metamaterial with an extremely high refractive index of 12.3 in the 0.3-THz band and apply it to a 3D phase delay component for high-performance gradient-index terahertz lenses. We also demonstrate a large-aperture robust polarizer with an extreme sensitivity of high extinction ratios below -50 dB consisting of a metamaterial with a large negative relative permittivity of -97.6. The 3D terahertz components utilizing unprecedented materials would contribute to the development of a future industry based on terahertz applications.

11:45 Tu-AM-6-3
Realizing Sub-diffraction Focusing For Terahertz

Ayato Iba1; Calvin W. Domier2; Makoto Ikeda1; Atsushi Mase3; Anh-Vu Pham2; Neville C. Luhmann, Jr2
1Sensing Technology Department, Asahi-Kasei Corporation, Japan; 2Department of Electrical and Computer Engineering, University of California, Davis, United States; 3Global Innovation Center, Kyushu University, Kasuga-koen, Japan

Measurement resolution is one of the most important elements for industrial applications. However, conventional lenses for terahertz (THz) or millimeter-wave cannot achieve high resolution due to the diffraction limit. Here, we demonstrate that two types of super-oscillatory lenses are very effective for subdiffraction focusing at THz.

12:00 Tu-AM-6-4
All-dielectric Guided-mode Resonance Filters In THz Region

Hyeon Sang Bark1; In Hyung Baek1; Kyu-Ha Jang1; young Uk Jeong1; Tea-In Jeon2
1Korea Atomic Energy Research Institute, Republic of Korea; 2Korea Maritime and Ocean University, Republic of Korea

In summary, because the proposed GMR filters have a high Q-factor, tunable filter and good polarizer characteristics, it has potential for THz applications in modulator, band pass filter, reflector, sensor [3] and bio-medical technologies in the future.

12:15 Tu-AM-6-5
Extraordinary THz Absorption In 2D Material-dielectric Integrated Metasurfaces

Sara Arezoomandan; Hugo Condori Quispe;
Berardi Sensale-Rodriguez
University of Utah, United States

This work discusses our recent findings on 2D material-dielectric integrated metasurfaces, as an alternative approach to 2D material-metal hybrid metamaterials, for providing efficient control of the electromagnetic beam propagation at THz wavelengths. The analyzed structures consist of a passive dielectric pattern and a reconfigurable 2D material sheet whose THz optical conductivity can be actively tuned. We show that via optimizing the geometric dimensions in the patterns it is possible to attain almost complete absorption by the 2D material at an arbitrary frequency of interest.

11:00 - 12:30 Tu-AM-7 Gas Spectro. & Sensing 2

Chairperson: Gaël Mouret Room 201

11:00 Tu-AM-7-1

High-resolution Fast Terahertz Time-domain Gas Spectroscopy Based On A Fine Comb Spectral Structure Of The NovoFEL
Vitaly Kubarev1; Yaroslav Getmanov1; Evgeny Chesnokov2; Pavel Koshlyakov2
1Budker Institute of Nuclear Physics, Russian Federation; 2Institute of Chemical Kinetics and Combustion, Russian Federation

High coherency and monochromaticity of the terahertz Novosibirsk Free-Electron Laser (NovoFEL) is appeared in very narrow comp spectral structure of its radiation (relative line's width is 2E-8, interval between lines is 5.6 MHz, total width of the comb-structure is 6-12 GHz). Sampling time-domain spectroscopy with resolution of order of the line width (~ 100 kHz) needs measuring time about of 20 µsec per one sampling point and only 56 slow sampling points to overlap the full NovoFEL comb spectrum. Shift of the comb structure will be made by changing of length of the NovoFEL optical resonator. Universal terahertz gas laser (line width ≤0.5E-8) will be used as local oscillator in the heterodyne spectrometer.

11:30 Tu-AM-7-2
Free Induction Decay Signals Stimulated By Photomixing

Fuanki Bavedila1; Guillaume Ducournau1; Jean-François Lampin1; Emilien Peytavit1; Arnaud Cuisset2; Gaël Mouret2; Cedric Bray3; Robin Bocquet2; Francis Hindle2
1IEMN CNRS/Université de Lille, France; 2Laboratoire de Physico-chimie de l'Atmosphère ULCO, France; 3Institut des Sciences Moléculaires Université de Bordeaux, France

An optically driven photoconductor device is electrically pulsed to provide a powerful pulse around 206 GHz. The pulsed radiation polarizes the OCS gas which emits a free induction decay signal that is observed after the end of the pulse. This is the first step in the development of a photonic chirped pulsed spectrometer.

11:45 Tu-AM-7-3
Terahertz Differential Absorption Spectroscopy Using Multi-Furcated Nd:YAG Microchip Laser For Gas Sensing
Yuma Takida1; Toshiyuki Ikeo2; Kouji Nawata1; Yoshio Wada2; Yasuhiro Higashi2; Hiroaki Minamide1
1RIKEN, Japan; 2Ricoh Company, Ltd., Japan

We demonstrate a frequency-domain differential absorption spectroscopy in the terahertz (THz) range for gas sensing applications. Our system is based on an injection-seeded THz-wave parametric generator driven by a multi-furcated Nd:YAG microchip laser. Within a single excitation cycle of the laser, the is-TPG generates up to three narrowband THz-wave pulses that are separated in time by 80 µs and in frequency by 11 GHz, which is due to the spatial hole burning effect in the laser cavity. These pulses can be directly used to measure differential absorption signals, and first and second derivative spectra of target gas molecules without measuring reference spectra.

12:00 Tu-AM-7-4
Determining DHO Detection Limits For A Frequency Domain THz Spectrometer Coupled To A Light-weight Multi-pass Sample Cell

Joseph Demers; Elijah Dale
Bakman Technologies, United States

A fringe-free, frequency domain terahertz spectrometer connected to a custom fabricated, light-weight multi-meter multi-pass sample cell was employed to measure the 1.492 THz, 1.507 THz and 1.523 THz molecular transitions of DHO over various pressures. We will report on the detectable concentrations of the DHO achieved with the portable instrument.

12:15 Tu-AM-7-5
THz/Far-IR Astrophysical Studies At The Australian Synchrotron

Dom Appadoo
ANSTO/Australian Synchrotron, Australia

THz synchrotron spectroscopy has become an important tool in the identification and quantification of molecular species of astrophysical interest; it is a routinely used technique as it is well established that synchrotron radiation offers a S/N advantage over conventional thermal sources. The brightness advantage is perfectly suited for high-resolution gas-phase spectroscopy, and at the Australian Synchrotron, this advantage is limited to energies lying below 1500 cm-1; however, a flux advantage is maintained for energies lying only below 350 cm-1 which facilitates the study of homogeneous condensed-phase samples. The THz/Far-IR beamline is equipped with a suite of both gas-phase and condensed-phase techniques to enable research on interstellar molecular species, and in this paper, the beamline capabilities available for the study of molecular species of astrophysical interest will be presented.

12:30-14:00 - Lunch

14:00-16:00 Parallel sessions Tu-PM1

14:00 - 16:00 Tu-PM1-1 Gyrotron 5

Chairperson: Alexander Litvak Amphi Lavoisier

14:00 Tu-PM1-1-1
Characterizing The Accelerating Mode Of A Dielectric-lined Waveguide Designed For Terahertz-driven Manipulation Of Relativistic Electron Beams

Vasileios Georgiadis1; Morgan Hibberd1; Alisa Healy2; Daniel Lake2; Graeme Burt2; Steven Jamison2; Darren Graham1
1The University of Manchester, The University of Manchester, Oxford Road, United Kingdom; 2University of Lancaster, University of Lancaster, Bailrigg, United Kingdom

We report on the generation of a terahertz beam with a quasi-TEM01 mode by exploiting the interferometric recombination of two linearly polarized emitters in a combined spintronic source. The generated THz beam was used to characterize the accelerating mode of a dielectric-lined waveguide (DLW) to inform on the recent demonstration of relativistic electron beam manipulation achieved with this THz-driven DLW at the CLARA research facility at Daresbury Laboratory.

14:30 Tu-PM1-1-2
First Operation Of Ka-band High-current Relativistic Gyrotron

Alexander Leontyev1; Edward Abubakirov1; Andrej Denisenko1; Alexey Fedotov1; Roman Rozental1; Vladimir Tarakanov2
1Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation; 2Moscow Engineering Physics Institute, Russian Federation

The results of the first operation of a pulse Ka-band gyrotron with output radiation power more than 110 MW are presented. The gyrotron was excited by electron beam with a current of up to 2 kA and particle energy of up to 500 keV, formed by an explosive emission cathode with subsequent transverse velocities pumping in a non-uniform field produced by a short coil (kicker) to a state with a pitch-ratio of about 1.

14:45 Tu-PM1-1-3
An Experimental Investigation Of A 0.8 THz Gyrotron With An Improved Mode Selection

Mikhail Glyavin1; Toshitaka Idehara2; Eduard Khutoryan3; Svilen Sabchevski4; et al1
1Institute of Applied Physics RAS, Russian Federation; 2FIR UF, Japan; 3IRE NASU, Ukraine; 4IE BAS, Bulgaria

In this paper, we present and discuss the latest experimental results from the investigation of the operational performance of a 0.8 THz double-beam gyrotron, which has been developed and manufactured recently in the framework of an international research project led by IAP-RAS and FIR UF. After the initial tests, the current experiments have been focused not only on the study of the operation at the design mode TE8,5 (at the second harmonic of the cyclotron frequency) but also of several other modes the generated radiation of which could be appropriate for various other applications besides the envisaged 1.2 GHz DNP-NMR spectroscopy. The obtained results give a deeper insight into the specifics of the operation of the double-beam gyrotron and especially on its capability to provide an improved mode selection and therefore a single mode second harmonic operation.

15:00 Tu-PM1-1-4
Observation Of Multi-Peak Frequency Spectrum In A High Power Sub-THz Gyrotron
Teruo Saito1; Shunsuke Tanaka1; Ryuji Shinbayashi1; Yuusuke Yamaguchi1; Masafumi Fukunari1; Yoshinori Tatematsu1; Maria Melnikova2; Nikita Ryskin2
1University of Fukui, Japan; 2Saratov State University, Russian Federation

Equi-distantly distributed multi-peak frequency spectrum was observed in a high power 300 GHz band gyrotron for the case of strong reflection off the vacuum window. An oscillation mode different from the design mode can oscillate by adjusting the magnetic field in the cavity. However, a large fraction of the output wave is reflected by the vacuum window. A theoretical calculation shows that the multi-peak frequency spectrum stems from periodic amplitude variation that is caused by mode competition between the oscillating co-rotating mode and the counter-rotating mode originating from the reflected wave.

15:15 Tu-PM1-1-5
Demonstration Of A High Power Frequency-Tunable 0.22-THz Gyrotron Operating In High-Order Axial Modes

Xiaotong Guan; Wenjie Fu; Dun Lu; Tongbin Yang; Xuesong Yuan; Yang Yan
University of Electronic Science and Technology, China

To explore the approach for generating high power frequency-tunable sub-THz to THz radiation, a 0.22-THz high-order axial modes (HOAMs) gyrotron is developed and tested in TRC-UESTC. The proof-of-principle experimental results demonstrate that a series of HOAMs in a long gyrotron cavity are excited successfully by an electron beam of high voltage and high current. A frequency tuning range of 0.79 GHz around 219 GHz has been achieved by tuning the operating magnetic field and operating in the first four axial modes. And during the frequency tuning, the out power kept no less than 0.45 kW, while the maximum output power was 3.80 kW. These experimental results of axial mode transition in high power sub-terahertz gyrotron should be conductive to the future development of frequency-tunable gyrotron towards some up-and-coming novel terahertz applications.

15:30 Tu-PM1-1-6
95 GHz Gyrotron With Water Cooled Magnet And High Average Power

Moritz Pilossof
Ariel University, Israel

Abstract-- A 95 GHz gyrotron with water cooled copper magnet delivering high average power was assembled. The cavity interaction mode is TE02 at the second cyclotron harmonic. Internal mode converter is used to convert the interaction mode to quasi-Gaussian mode at the gyrotron output window. A ~1.8T magnetic field is produced by water cooled copper electro-magnet. The magnet and the gyrotron have immediate turn on and off time when the cathode is worm (<1s). Initial results will be presented.

15:45 Tu-PM1-1-7
Multibeam And Multibarrel Gyrotrons

Vladimir Zapevalov; Vladimir Zapevalov
Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

The report analyzes the perspective of multibeam and multibarrel version of gyrotron for possibility of frequency tuning and improved mode selection at gyrotron working on the gyrofrequency harmonics.

14:00 - 16:00 Tu-PM1-2 Solid State 4

Chairperson: Dmitry Khokhlov Petit Amphi

14:00 Tu-PM1-2-1

Infrared/Terahertz Photogalvanic Spectroscopy Of Three And Two Dimensional Topological Insulators
Sergey Ganichev
Terahertz Center, University of Regensburg, Germany

The paper overviews experimental and theoretical studies of photogalvanic and photon drag effects induced in various in three-dimensional (3D) and 2D topological insulators (TI) by polarized infrared/terahertz (IR/THz) radiation. e present the state-of-the-art of this subject, including both recent advances and well-established results. Various physical mechanisms of photogalvanic and photon drag effects in TI systems are described including experimental achievements, phenomenological description, models visualizing physics of nonlinear responses, and microscopic theory of individual effects. Several examples for the characteristics determined by applying photocurrents are: the Fermi velocity, the cyclotron masses as a function of carrier density and temperature, the orientation of surface domains in 3D TIs, and the surface state mobility.

14:30 Tu-PM1-2-2
Terahertz Electron Paramagnetic Resonance Spectroscopy using An Ultrathin Membrane Device

Eiji Ohmichi; Hideyuki Takahashi; Tsubasa Okamoto; Daiki Hachiya; Hitoshi Ohta
Kobe University, Japan

A novel terahertz (THz) electron paramagnetic resonance (EPR) spectroscopy technique is presented. The use of an ultrathin membrane device allows sensitive EPR detection of small volume samples in the frequency region up to 0.65 THz. We show THz EPR spectroscopy results on microliter solution of myoglobin and a tiny single crystal of a magnetically ordered sample.

14:45 Tu-PM1-2-3
Influence Of Cu-doping On Terahertz Conductivity And Temperature-driven Phase Transition In NdNiO3 Thin Films

Mahesh Chandra
1; V. Eswara Phanindra2; S. Prabhu3; Krushna Mavani1
1Indian Institute of Technology Indore, India; 2Indian Institute of Science Education and Research Bhopal, India; 3Tata Institute of Fundamental Research, India

Perovskite nickelates show the first order metal-insulator transition. Doping of 3d metal ions at Ni-site can drastically change the electronic properties. We have deposited and studied Cu-doped NdNiO3 thin films for structural and electronic properties. Merely 2% Cu-dopingat Ni-site induces a metallic state in otherwise insulating NdNiO3 film at low temperatures. The terahertz conductivity shows Drude behavior and the conductivity is tuned by Cu-doping in these films.

15:00 Tu-PM1-2-4
Calculating The Complex Permittivity Of Powdered Crystalline Materials

Andrew Burnett; Calum Towler; John Kendrick
School of Chemistry, University of Leeds, United Kingdom

Solid-state density functional theory calculations including periodic boundary conditions have become well established for calculating the THz spectra of crystalline materials. Here we compare a range of DFT programs and calculation parameters including a number of van der Waals' dispersive corrections in combination with our post-processing tool, PDielec, to calculate the complex permittivity of a range of powdered crystalline materials.

15:15 Tu-PM1-2-5
Spin And Lattice Dynamics Of Multiferroic SrMn7O12 Studied By THz And Infrared Spectroscopies At Low Temperatures And In Magnetic Field

Filip Kadlec1; Veronica Goian1; Dmitry Nuzhnyy1; Christelle Kadlec1; Jakub Vít1; Fedir Borodavka1; Iana S. Glazkova2; Alexei A. Belik3; Stanislav Kamba1
1Institute of Physics CAS, Czech Republic; 2Lomonosov Moscow State University, Russian Federation; 3National Institute for Materials Science, Japan

Multiferroic SrMn7O12 crystals are isostructural with CaMn7O12 which is known for its unusual symmetry properties and a record-high spin-induced polarization. We studied SrMn7O12 ceramics by THz time-domain and Fourier-transform infrared spectroscopies upon varying temperature and magnetic field. In the magnetic phases, we observed spin waves gaining strength from phonons; thus, they are assigned to electromagnons. We discuss the observed persistence of several low-temperature vibrational modes above the high-temperature phase transition, and the impact of atomic substitution with regard to CaMn7O12.

15:30 Tu-PM1-2-6
Identification And Characterization Of 'Killer-Modes' In Organic Semiconductors With Terahertz Spectroscopy

Peter Banks; Michael Ruggiero
The University of Vermont, United States

Organic semiconductors are promising modern optoelectric materials, with countless potential applications ranging from flexible displays to photovoltaics. The applicability of these materials is largely driven by their charge carrier mobility, which is strongly influenced by low-frequency vibrations. In this work, the specific low-frequency vibrations that exhibit strong electron-phonon coupling, deemed 'killer-modes', in organic semiconductors are determined using a combination of terahertz time-domain spectroscopy and solid-state density functional theory. The results of this study enable a concerted synthetic effort to rationally design novel materials, utilizing intermolecular forces to stiffen lattice dynamics, to ultimately improve charge carrier mobility.

15:45 Tu-PM1-2-7
Effects Of Low Content Enantiomer Impurity In L-histidine Crystal Observed By Terahertz Spectroscopy

Tetsuo Sasaki1; Tomoaki Sakamoto2; Makoto Otsuka3
1Shizuoka University, Japan; 2National Institute of Health Sciences, Japan; 3Musashino University, Japan

Effects of enantiomer impurity molecule at low content on THz spectrum were studied. L-histidine crystal was grown controlled to monoclinic form B from ethanol-rich solvent. D-histidine was added in the range 0.05 to 10.0 % in the solvent before recrystallization. Peak frequency shifts of absorption lines of L-histidine at 10 K on the relation with D-histidine content were evaluated by high frequency accurate THz spectrometer. It was shown that high sensitive detection of enantiomer impurity was possible until DL racemic compound crystal was formed with increasing D-histidine content.

14:00 - 16:00 Tu-PM1-3 THz Devices 1

Chairperson: Stefano Barbieri Room 162

14:00 Tu-PM1-3-1

Free-space Coupling Of Terahertz Whispering-gallery Modes
Dominik Vogt; Angus Jones; Rainer Leonhardt
University of Auckland, New Zealand

We report on free-space coupling of high quality (Q) spherical THz whispering-gallery mode resonators (WGMRs) as a simple alternative to more complex waveguide and prism coupling. Excitation efficiencies up to 50% to WGMs with Q-factors of 1.5x10^4 at 0.7THz are achieved.

14:30 Tu-PM1-3-2
Terahertz Polarization Splitter Based On Parallel-plate Waveguide Technology

Arturo Hernandez-Serrano; Emma Pickwell-MacPherson
University of Warwick, United Kingdom

In this work we present a terahertz polarization splitter based on a parallel-plate waveguide (PPWG). The proposed structure consists of a stacked array of stainless steel plates with 0.8mm spacing. The device is capable of splitting the two orthogonal polarization components (TM and TE) in a frequency range of 250GHz to 500GHz.

14:45 Tu-PM1-3-3
High-Performance Frequency Selective Surface Filters For Terahertz Applications

Sergei Kuznetsov1; Nazar Nikolaev2; Andrey Arzhannikov3
1Rzhanov Institute of Semiconductor Physics SB RAS, Russian Federation; 2Institute of Automation and Electrometry SB RAS, Russian Federation; 3Budker Institute of Nuclear Physics SB RAS, Russian Federation

We review the results of extensive R&D activity focused on elaborating high-performance quasi-optical filters using the technology of frequency selective surfaces. The band-pass, low-pass, and high-pass devices operating at subterahertz and terahertz frequencies are described. The issues of design optimization, lithographic fabrication, and spectral characterization of the developed filters alongside with their practical applications are considered.

15:00 Tu-PM1-3-4
Giant Dual-mode Graphene-based THz Modulator

Liang-Hui Du1; Pei-Ren Tang2; Jiang Li1; Li-Guo Zhu1
1Institute of Fluid Physics, China Academy of Engineering Physics, China; 2University of Science and Technology of China, China

We report a high-performance terahertz (THz) modulator with dual-operation mode. For the pulse operation mode, the proposed THz modulator has the advantage of high modulation depth (MD) and can operate in a broadband frequency range. We have experimentally achieved a MD larger than 90% for the fifth-order pulse THz echo at 0.8 THz and the MD stays larger than 75% in a broadband frequency range larger than 1 THz. While, for the coherent operation mode, the Fabry-Perot (F-P) interference effect has been taken into consideration and a MD larger than 75% at 0.76 THz has also been realized.

15:15 Tu-PM1-3-5
Photonic Bandgap Bragg Waveguide-based Terahertz Microfluidic Sensor

Yang Cao; Kathirvel Nallappan;
Hichem Guerboukha; Thomas Gervais; Maksim Skorobogatiy
Polytechnique Montreal, Canada

A 3D printed photonic bandgap Bragg waveguide-based resonant microfluidic sensor operating in the THz spectral range is theoretical analyzed and experimental studied. The analytes are injected into a microfluidic channel to a defect layer region which results in a modal anti-crossing phenomenon. By tracking the spectral positions of the induced absorption dips and phase changes of the transmission spectra of various liquids, we measure a sensitivity of 110 GHz/RIU. The proposed sensor features high reliability and can provide a non-contact measurement method for real-time monitoring of the refractive index change of liquid flow in practical applications.

15:30 Tu-PM1-3-6

Efficient Ultrafast THz Modulators Based On Negative Photoconductivity In Controllably Doped Carbon Nanotubes

Burdanova, Maria1; Tsapenko, Alexey2; Satco, Daria2; Kashtiban, Reza1; Mosley, Connor3; Monti, Maurizio1; Staniforth, Michael1; Sloan, Jeremy1; Gladush, Yuriy2; Nasibulin, Albert2; Lloyd-Hughes, James1
1The University of Warwick, United Kingdom ; 2Skolkovo Institute of Science and Technology, Russian Federation

Large diameter single-walled carbon nanotubes films are shown to have a doping level and THz conductivity that can be readily controlled using adsorption doping or electrostatic gating. The giant negative photoconductivity observed upon optical excitation is due to a rapid reduction in mobile carrier density, synchronously to a lowering of the momentum scattering rate. The large modulation depth and tunable recovery time open prospects for carbon nanotube films in ultrafast and THz devices.

15:45 Tu-PM1-3-7
Engineered Silicon For Efficient Mm-Wave And THz Modulators

Lauren Barr1; Ian Hooper1; Nicholas Grant2; Samuel Hornett1; Christopher Lawrence3; John Murphy2; Euan Hendry1
1University of Exeter, United Kingdom; 2University of Warwick, United Kingdom; 3QinetiQ, United Kingdom

Large diameter single-walled carbon nanotubes films are shown to have a doping level and THz conductivity that can be readily controlled using adsorption doping or electrostatic gating. The giant negative photoconductivity observed upon optical excitation is due to a rapid reduction in mobile carrier density, synchronously to a lowering of the momentum scattering rate. The large modulation depth and tunable recovery time open prospects for carbon nanotube films in ultrafast and THz devices

14:00 - 16:00 Tu-PM1-4 Telecom 2

Chairperson: Guillaume Ducournau Room 269

14:00 Tu-PM1-4-1

12.5-Gbit/s Wireless Link At 720 GHz Based On Photonics
Tadao Nagatsuma1; Masato Sonoda1; Taiki Higashimoto1; Li Yi1; Jeffrey Hesler2
1Osaka University, Japan; 2Virginia Diodes, Inc., United States

This paper addresses a development of 600-GHz band wireless links based on photonics technologies. An error-free transmission at a bit rate of >12.5 Gbit/s has been demonstrated for the first time at 720 GHz using a photodiode-based transmitter and a Schottky-barrier-diode mixer receiver.

14:30 Tu-PM1-4-2
The Influence Of RF Front-End Imperfections On Performance Of A 220- 260 GHz Tunable M-QAM Wireless Link In SiGe HBT Technology
Janusz Grzyb1; Pedro Rodriguez Vazquez1; Bernd Heinemann2; Ullrich Pfeiffer1
1University of Wuppertal, Germany; 2IHP- Leibniz-Institut für Innovative Mikroelektronik, Germany

This paper presents system-level characterization and performance evaluation for higher-order M-QAM modulation formats of a fully-electronic 1-m wireless link with two highly-integrated direct-conversion quadrature TX and RX modules in 0.13-υm SiGe HBT technology operating with a tunable 220-260 GHz LO carrier. With the limited baseband bandwidth of 15 GHz, the maximum achieved data rates for 16-/32-/64-QAM modulation are 90 Gbps (EVM of 14.6%), 90 Gbps (EVM of 11.9%) and 81 Gbps (EVM of 8.7%), respectively.

14:45 Tu-PM1-4-3
A Metal Wire Waveguide For Terabit DSL

Rabi Shrestha1; Kenneth Kerpez2; Chan Soo Hwang2; Mehdi Mohseni2; John Cioffi2; Daniel M. Mittleman1
1Brown University, United States; 2ASSIA, Inc., United States

We investigate the propagation of terahertz radiation on a complex multi-element metal wire waveguide ensheathed in a metal jacket. Mode mixing due to bends and nonuniformities along the waveguide axis result in a nearly random mode pattern at the output. This stochastic mixing is ideal for a vectored transmission, analogous to the multiple-input, multiple-output (MIMO) concept commonly used in wireless networking and could enable terabit-per-second data rates on the existing cables already in use by DSL systems.

15:00 Tu-PM1-4-4
PIN Photodiode Emitter For 32 GBd 16QAM Wireless Link At 300 GHz

Simon Nellen; Carlos Castro; Lars Liebermeister; Robert B. Kohlhaas; Robert Elschner; Colja Schubert; Martin Schell; Bjoern Globisch; Bjoern Globisch; Ronald Freund
Fraunhofer HHI, Germany

We demonstrate a wireless data link at 300 GHz employing a broadband PIN photodiode as the emitter. With a symbol rate of 32 GBd and QPSK modulation error-free transmission at a gross data rate of 64 Gbit/s is achieved. For 16QAM modulation, forward error correction enables a net data rate of 100 Gbit/s, which is among the highest values reported so far.

15:15 Tu-PM1-4-5
300 GHz Wireless Communication Systems Exploiting The Benefits Of Combining Photonic And Electronic Transceiver Components

Ingmar Kalfass
1; Iulia Dan1; Pascal Szriftgiser2; Vinay-Kumar Chini3; Mohammed Zaknoune3; Guillaume Ducournau3
1Institute of Robust Power Semiconductor Systems, Univ Stuttgart, Germany; 2PhLAM, France; 3IEMN CNRS/Université de Lille, France

The contribution presents a wireless data transmission experiment combining photonic and electronic technologies. The photonic transmitter is based on the use of uni-traveling-carrier (UTC) photodiodes. The electronic receiver is based on multi-functional monolithic integrated circuits realized in high electron mobility transistor (HEMT) technology for low-noise pre-amplification as well as integrated I/Q detection. The combination of both is interesting towards the achievement of larger distances and high data-rates for future THz links. In this paper we present an initial experiment where 80 Gbit/s were achieved, carried out in the context of a join French-German research initiative.

15:30 Tu-PM1-4-6
300 GHz-band 50 Gbit/s Dual Channel Link Using Industrial Silicon Photonics Technology

Cybelle Belem
1; Elsa Lacombe2; Vincent Gidel2; Cedric Durand2; Frederic Gianesello2; Daniel Gloria2; Cyril Luxey3; Guillaume Ducournau1
1IEMN CNRS/Université de Lille, France; 2STMicroelectronics, France; 3Polytech'Lab, Univ Nice Sophia, France

We demonstrate the use of an industrial silicon photonics photodiode towards indoor THz links in the 300 GHz band. The devices are presented and two links are reported: the first one in a single channel operation QPSK-25 Gbit/s signaling and the second one using a dual channel configuration, 260 and 280 GHz, reaching 50 Gbit/s. In each case, the detection is done using a III-V GaAs Schottky-based sub-harmonic mixer.

15:45 Tu-PM1-4-7
Millimeter Wave Vacuum Electronic Amplifiers For High Data Rate Communication

PAN PAN; Zhangxiong Zi; Ji Chen; Shishuo Liu; Qingmei Xie; Ye Tang; Jun Cai; Jinjun Feng
Beijing Vacuum Electronics Research Institute, China

Traveling wave tubes, one kind of vacuum electronic amplifiers, have been widely used in radars and satellite communications. For its capability to provide high output power in millimeter wave regime, traveling wave tubes are an enabling technology for outdoor long-range high data rate communication. Traveling wave tubes operating at E-band, W-band and G-band are being developed and the experimental results of prototypes are presented.

14:00 - 16:00 Tu-PM1-5 Nano-quantum Devices 1

Chairperson: Room 101

14:00 Tu-PM1-5-1

Ultra-Small Mode Volume Three-Dimensional THz LC Metamaterial
Mathieu Jeannin1; Djamal Gacemi1; Angela Vasanelli1; Lianhe Li2; Edmund Linfield2; Carlo Sirtori1; Yanko Todorov1
1Ecole Normale Supérieure, France; 2School of Electronics and Electrical Engineering, University of Leeds, United Kingdom

We present a novel architecture for THz metamaterials relying on three-dimensional meta-atoms embedding a semiconductor active region. The meta-atoms behave as inductor-capacitive (LC) resonators with nano-scale capacitive parts, and they have extremely sub-wavelength mode volume (10^-6λ_0) and footprint (10^-3λ_0^2). When the LC resonators are coupled to a two-dimensional electron gas confined inside the capacitive elements the ultra-strong light-matter coupling regime is achieved. We also discuss the potential of such structures for ultra-low dark current THz quantum well photodetectors.

14:30 Tu-PM1-5-2
High Performance Graphene Ballistic Rectifiers For THz Detection

Jiawei Zhang;
Joseph Brownless; Aimin Song
University of Manchester, United Kingdom

Although graphene can operate in the ballistic transport regime at room temperature, there are very few devices harnessing this property. Here we present a novel device called the ballistic rectifier which circumvents the problem of opening a bandgap in graphene. Based on the device theory, we proposed four different asymmetric planar structures. All devices are working and showed responsivity higher than 1,000 V/W at room temperature, with noise-equivalent power as low as 4.16 pW/Hz^1/2. These properties make GBRs a suitable candidate for THz detections.

14:45 Tu-PM1-5-3
Ultrastrong Coupling Of Plasmonic Metamaterials And Photons In A Terahertz Photonic Crystal Cavity

Fanqi Meng; Mark D. Thomson; Bernhard Klug; Dovilė Čibiraitė; Qamar ul-Islam; Hartmut G. Roskos
J. W. Goethe-Uni Frankfurt, Germany

Here, we report a new type of strong light-matter interaction of metamaterial 'quasi-particles' with photons in a photonic crystal cavity in the terahertz frequency range. The measured Rabi splitting shows a square-root dependence on the density of metamaterial unit cells, even for unit cells from two spatially separated planar metamaterials, indicating nonlocal collective strong interactions. These findings are of interest for the investigation of fundamental strong-coupling phenomena, but also for applications such as ultra-low-threshold terahertz polariton lasing, voltage-controlled modulators and frequency filters, and ultra-sensitive chemical and biological sensing.

15:00 Tu-PM1-5-4
Towards Millimeter-Wave Based Quantum Networks

Hubert Stokowski1; Marek Pechal1; Emma Snively2; Kevin Multani1; Paul Welander2; Jeremy Witmer1; Emilio Nanni2; Amir Safavi-Naeini1
1Stanford University, United States; 2SLAC National Accelerator Laboratory, United States

Realization of quantum networks composed of superconducting microwave circuits acting as qubits recently gained tremendous attention as an effective way of scaling quantum computers. Here we present the first experimental approach to fabricate mm-wave superconducting resonators that could be combined with transmon qubits and used in future ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'ââ,¬Â¦Ãfâ?sÃ,½ÃfÆ'Ã?â?TÃf¢ââ?s¬Ã.¡ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,¼m-mm converters that distribute entanglement at a high rate in low-loss quantum networks. We propose a method that facilitates a long-range spread of quantum information via direct coupling of such a device into W-band (75-110 GHz) waveguide.

15:15 Tu-PM1-5-5
Sliver Nanowire Surface Plasmon Polaritons Enhancement In Terahertz Nanodevices

Shihab Al-Daffaie1; Oktay Yilmazoglu1; Matthias Wiecha2; Amin Soltani2; Franko Küppers1; Thomas Kusserow1; Hartmut Roskos2
1Technische Universität Darmstadt, Germany; 2Goethe-Universität, Germany

New types of continuous-wave (CW) THz photomixers were fabricated using a silver nanowire (Ag-NW) as nanocontact on low-temperature-grown (LTG) and nitrogen-ion-implanted GaAs, respectively. The Ag-NW nanoelectrodes produced a large reduction of the device capacitance and a significant enhancement of the photocurrent as compared to conventional photomixers. The combination of very low capacitance and high photocurrent are shown reliable and efficient THz generation in the upper part of the broad spectral THz range. The main enhancement is shown from the wave patterns of surface plasmon polaritons (SPPs) on the Ag-NW which are measured using a scattering-type Scanning Near-field Optical Microscope (s-SNOM).

15:30 Tu-PM1-5-6
Nano-FTIR Spectroscopy Of Intersubband Polaritons In Single Nanoantenna

Oleg Mitrofanov1; Chih-Feng Wang2; Terefe Habteyes2; Willie Luk3; John Klem3; Hou-Tong Chen4; Igal Brener3
1UCL, United Kingdom; 2University of New Mexico, United States; 3CINT, Sandia NL, United States; 4CINT, Los Alamos National Lab, United States

We demonstrate observation of infrared (IR) intersubband (ISB) polaritons in an isolated subwavelength size nanoantenna using near-field Fourier-transform infrared (FTIR) spectroscopy of the evanescent fields on the nanoantenna surface. The near-field approach enables detection of the distinctive polariton splitting of the nanoantenna resonance in the amplitude and phase spectra, as well as mapping of the ISB polariton dispersion. The nano-FTIR spectroscopy approach opens doors for investigations of light-matter interaction in the single subwavelength nanoantenna regime.

15:45 Tu-PM1-5-7
Semiconductor Quantum Plasmonics

Angela Vasanelli1; Simon Huppert2; Andrew Haky1; Yanko Todorov1; Carlo Sirtori1
1Ecole Normale Supérieure, France; 2Sorbonne Université, France

We investigate the effect of quantum confinement on plasmons in highly doped semiconductor layers. The collective response of the electron gas is constructed from the basis of the confined electronic wavefunctions, accounting for dipole-dipole coupling and non-parabolicity. Our work shows how quantum engineering can be applied to semiconductor plasmonics.

14:00 - 16:00 Tu-PM1-6 Metamarials 2

Chairperson: Aydin Babakhani Room 151

14:00 Tu-PM1-6-1

Spectroscopic Evidence Of Bloch Surface Waves In The Mid Infrared
Michele Ortolani1; Marialilia Pea2; Agostino Occhicone3; Valeria Giliberti4; Alberto Sinibaldi3; Francesco Mattioli2; Sara Cibella2; Raffaella Polito1; Alessandro Nucara1; Leonetta Baldassarre1; Francesco Michelotti3
1Sapienza University of Rome, Dipartimento di Fisica, Italy; 2Consiglio Nazionale delle Ricerche (CNR), Italy; 3Sapienza University of Rome, Dipartimento SBAI, Italy; 4Istituto Italiano di Tecnologia, Center for Life Nanoscience, Italy

Bloch Surface Waves (BSWs) are surface electromagnetic waves with very low intrinsic losses, existing in both in-plane and out-of plane polarizations, supported by a one-dimensional photonic crystal with an in-gap defect. We have developed thin film deposition technology on CaF2 prisms suitable for biosensing applications of BSWs in the mid-infrared. Here we report spectroscopic evidence of BSWs, in perfect agreement with theory, in the wavelength range from 4 to 6 micrometers. In summary, we envisage Surface Plasmon Polarioton-like biosensing applications, in which the mid-IR fingerprints of thin samples located at the interface are detected with high sensitivity by Bloch Surface Waves instead of SPPs.

14:30 Tu-PM1-6-2
High Q-factor Coupled Fabry-Perot Plasmonic Nanoresonator
Baptiste FIX1; Julien Jaeck1; Patrick Bouchon1; Nathalie Bardou2; Sébastien Héron1; Benjamin Vest1; Haïdar Riad1
1ONERA, France; 2C2N-CNRS, France

Fabry-Perot (FP) like resonances have been widely described in nanoantennas. In the case of combination of nanoantennas, it has been reported that each cavity behaves independently. Here, we evidence the interferences between two FP absorbing nanoantennas, which has a strong impact on the optical behavior. While the resonance wavelength is only slightly shifted, the level of absorption reaches nearly 100%. Moreover, the quality factor increases up to factor 7 and can be chosen by geometric design over a range from 11 to 75. We first demonstrate thanks to a simple analytical model that this coupling can be ascribed to a double FP cavity resonance, with the unique feature that each cavity is separately coupled to the outer medium. Based on this principle, we experimentally illustrate the existence of a high-Q factor resonance originating from the interference between two under-coupled ribbon-shaped nano Fabry-Perot.

14:45 Tu-PM1-6-3
Study Of Terahertz High Q-factor All-Dielectric Metamaterials
Xiaoyong He; Jun Peng
Mathematics & Science College, Shanghai Normal University, China

The propagation properties of Si based all-dielectric metamaterials (ADMs) structure have been investigated systematically in the THz regime. The results manifest that ADMs indicate sharp resonant curves with large Q-factors of more than 60, and figure of merit is about 20. Compared with that of metal metamaterials counterparts, the thickness of ADMs (in the range of tens of micrometers) is much larger to excite obvious resonant curves. With the help of a uniform graphene layer, the resonant curves can also be flexible modulated in a wide range, the amplitude modulation depth can reach about 40%. The results are very useful to design high Q-factor dielectric devices in the future, e.g. biosensors, modulators, and filter.

15:00 Tu-PM1-6-4
Modes And Pseudo-modes In TE Extraordinary THz Transmission

Suzanna Freer
1; Miguel Camacho2; Sergei A Kuznetsov3; Eve Shalom1; Jack Gape1; Rafael R Boix4; Miguel Beruete5; Miguel Navarro-Cia1
1University of Birmingham, United Kingdom; 2University of Exeter, United Kingdom; 3Rzhanov Institute of Semiconductor Physics SB RAS Novosibirsk Branch TDIAM, Russian Federation; 4University of Seville, Spain; 5Universidad Pública de Navarra, Spain

Transverse electric (TE) transmission through dielectric-backed subwavelength slit arrays is inextricably linked to the grounded-dielectric slab TE1 mode, and thus, it depends highly on the electrical thickness of the substrate. We track the influence of the TE1 mode using both Terahertz time domain spectroscopy (TDS) measurements and the Method of Moments. For electrically thick dielectric samples, the TE1 mode is in propagation, and hence total transmission occurs (in excess of 0 dB, attributed to collimation), whereas in electrically thin samples, the TE1 mode is in cutoff. In this regime, the mode still contributes to transmission, and hence is referred to as a pseudo-mode.

15:15 Tu-PM1-6-5
Fano Resonance In Terahertz Superconducting Tl2Ba2CaCu2O8 Metamaterials

Jingbo Wu1; Yun Guan1; Jian Xing2; Lu Ji2; Caihong Zhang1; Huabing Wang1; Biaobing Jin1; Jian Chen1; Peiheng Wu1
1Nanjing University, China; 2Nankai University, China

Tl2Ba2CaCu2O8 is layered cuprate superconductor with high anisotropy. Using Tl2Ba2CaCu2O8 film and asymmetric resonator structure, we designed and fabricated a kind of terahertz metamaterials. The tuning of the Fano-type resonance with the change of temperature is experimentally demonstrated.

15:30 Tu-PM1-6-6
Manipulation On Terahertz Slow Light In Symmetry Broken Meta-molecules

Zhenyu Zhao1; Wei Peng2; Jianbing Zhang2
1Shanghai Normal University, China; 2Chinese Academy of Sciences, China

We investigate slow light effect owing to the plasmon-induced transparency (PIT) via symmetric breaking in terahertz meta-molecules (MM). A broadband PIT window as well as a localized slow light effect is achieved via conductively coupled dimer and trimer MM.

15:45 Tu-PM1-6-7
Ultrastrong Coupling Experiments With Superradiant Meta-atoms

Moritz Wenclawiak; Benedikt Limbacher; Aaron M. Andrews; Gottfried Strasser; Karl Unterrainer; Juraj Darmo
TU Wien, Austria

In this contribution, we study the effects arising when using a metamaterial surface featuring a dense array of superradiant emitters as cavities for experiments in the ultrastrong coupling regime. We show that an increasing cavity loss does not always lead to the expected transition to the weakly coupled Purcell regime but more that it is still possible to observe polaritons as a feature of the strong coupling between the meta-atoms and the intersubband transition.

15:45-16:15 - Coffee Break

16:30-18:15 Parallel sessions Tu-PM2

16:30 - 18:15 Tu-PM2-1 Films and Coatings

Chairperson: Michael Johnston Amphi Lavoisier

16:30 Tu-PM2-1-1
Investigation Of Multilayered 20th Century Painting By THz Imaging
Kaori Fukunaga1; Yoshimi Ueno2; Yasunobu Ito3
1National Institute of Information and Communications Technology, Japan; 2CRS Corporation, Japan; 3Ikea Museum of 20th Century Art, Japan

A masterpiece of Salvador Dali was investigated by using Terahertz time-domain imaging. The experimental results confirmed its multilayered structure and suggested that Dali did not cover the entire canvas because the number of painted layers depends on the area. The painting was supported with a lining layer and a metal plate added in previous intervention, and its structure was compared with that of another 20th century masterpiece painted by Pablo Picasso.

17:00 Tu-PM2-1-2
Mobile Handheld FMCW Terahertz Multilayer Thickness Inspection
Nina Schreiner; Stefan Weber; Andreas Keil; Fabian Friederich
Fraunhofer ITWM, Germany

We present an all-electronic handheld system for the thickness determination of dielectric multilayer structures with submillimeter to several centiÃ,¬meter layer thicknesses, using a frequency-modulated continuous-wave terahertz transceivers. Besides A-scans, an integrated linear position encoder allows to obtain B-scan images. In order to resolve layers below the inherent resolution limit given by the frequency modulation bandwidth, we take advantage of model-based signal processing techniques.

17:15 Tu-PM2-1-3
Ancient Painting On Copper Substrate Inspected By Terahertz Spectroscopy-imaging
Quentin Cassar1; Corinna Koch-Dandolo2; Jean-Paul Guillet1; Marie Roux3; Frédéric Fauquet1; Patrick Mounaix1
1Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France; 2C2MRF / Palais du Louvre, France; 3L'Atelier des Renaissances, France

We used a combination of numerical simulation to find parameters that best describe reflections from a given multi-layered paint sample. The reflected terahertz time domain waveform is simulated where each paint layer is represented by a set of numerical parameters that describe both the thickness and the optical response. We detected numerous sketches under the painting layers.

17:30 Tu-PM2-1-4
Operational Readiness Levels For Terahertz Automotive Paint Inspection
Robert May; Ian Gregory; Daniel Farrell
TeraView Ltd., United Kingdom

The demanding requirements placed on industrial test equipment means that for terahertz sensing to be adopted in quality control sectors, the technology must not only be capable of providing the qualitative and/or quantitative information of interest, but to do so in a robust and reliable manner. Here, we report on some of the developments implemented to bridge this gap for terahertz sensing to be deployed into one such industrial production setting: coating thickness inspection in the automotive paint shop. This has allowed terahertz to provide feedback on paint film thicknesses, and thereby allow for greater control of the paint process. Application Readiness, as defined by key manufacturers, their distributors and integrators, has been achieved.

17:45 Tu-PM2-1-5

Terahertz Non-Destructive Thickness Characterization Of Optically Thin Wu?stite Layers On Steel
David Citrin1; Alexandre Locquet1; Roquelet Cyrielle2; Min Zhai1
1Georgia tech Lorraine, France; 2ArcelorMittal Maizières Research, France

Terahertz (THz) imaging is a relatively new technique for nondestructive evaluation. Compared with the destructive micro-cut technique that provides information along the line of cut only, THz imaging nondestructively provides a global mapping of a sample. Hence, this technique has been applied to characterize coated materials and composite laminates. In this work, we characterize optically thin wüstite layers on steel leveraging signal-processing techniques.

18:00 Tu-PM2-1-6

Learning-Based Shadow Mitigation For Terahertz Multi-Layer Imaging
Pu (Perry) Wang1; Toshiaki Koike-Akino1; Arindam Bose2; Rui Ma1; Phillip Orlik1; Wataru Tsujita3; Kota Sadamoto3; Hiroyuki Tsutada3
1Mitsubishi Electric Research Laboratories, United States; 2University of Illinois at Chicago, United States; 3Mitsubishi Electric Corporation Advanced Technology R&D Center, Japan

This paper proposes a learning-based approach to mitigate the shadow effect in the pixel domain for Terahertz Time-Domain Spectroscopy (THz-TDS) multi-layer imaging. Compared with model-based approaches, this learning-based approach requires no prior knowledge of material properties of the sample. Preliminary simulations confirm the effectiveness of the proposed method.

16:30 - 18:30 Tu-PM2-2 Applications 1

Chairperson: René Beigang Petit Amphi

16:30 Tuo-PM2-2-1
Remote Liquid Inspection With Carbon Nanotube Terahertz Detectors
Meiling Sun; Kou Li; Yu Tokumoto; Ryogo Utaki; Yukio Kawano
Tokyo Institute of Technology, Japan

High installation cost, low temperature operation and strict measuring condition have been technical difficulties on terahertz (THz) wave inspections, which severely pulled back the development of THz wave application in real life. Here, to realize much quicker and lower-cost quality inspection in terahertz region, we developed a novel type of compact remote quality inspection system without conventional bulky THz time-domain spectroscopy (THz-TDS) system by utilizing a thermoelectric THz imager based on carbon nanotube (CNT) films. The present scheme enabled us to realize well applicable THz wave inspections.

17:00 Tu-PM2-2-1
Terahertz Diagnostics At Accelerators Using Radio Frequency-driven Frequency Combs Based On Telecommunication Technology
Erik Bruendermann1; Johannes Leonhard Steinmann1; Isao Morohashi2; Shinya Nakajima2; Shingo Saito2; Norihiko Sekine2; Anke-Susanne Mueller1; Iwao Hosako2
1Karlsruhe Institute of Technology / IBPT, Institute for Beam Physics and Technology, Germany; 2National Institute of Information and Communications Technology, Japan

We report on exploiting information and communications technologies to build reliable and durable terahertz diagnostics for electron accelerator-based light and laser sources. Terahertz and electro-optical diagnostics is an ideal tool to investigate short-bunch electron beams and their emitted photons with the potential to devise methods for controlled and tailored radiation emission. We investigate electro-optical modulators to evaluate their potential for laser-based diagnostics at accelerators, which can serve as building blocks in frequency combs, terahertz generation and detection systems. We built a frequency comb spanning at least 250 GHz with a pulse length of less than 3.7 ps.

17:15 Tu-PM2-2-3
Spoilage Of Salmon Fillets As Observed By THz Waves
Francis Hindle1; Lotta Kuuliala2; Meriem Mouelhi1; Arnaud Cuisset3; Mathias Vanwolleghem4; Frank Devlieghere5; Gael Mouret3; Robin Boquet3
1Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, France; 2Research Unit Food Microbiology and Food Preservation, Department of Food Technology, Ghent University, Belgium; 3Laboratoire de Physico-Chimie de l'Atmosphère, France; 4Institute of Electronics, Microelectronics and Nanotechnology, University of Lille, France; 5Research Unit Food Microbiology and Food Preservation, Ghent University, France

The minimization of food wastage is an important challenge for today's society. Microbial activity during the storage of foodstuffs packed under a protective atmosphere, will lead to the generation of a complex mixture of trace gases that may be used as food spoilage indicators. THz waves have been used to monitor the generation of hydrogen sulfide in the headspace of a sealed plastic tray containing a salmon fillet portion.

17:30 Tu-PM2-2-4
Towards Detection Of Helical Orientated Cellulose Structures In Wood Using THz Time-Domain Spectroscopy
Jingming Cao1; Markus Rüggeberg2; Peter Zolliker3
1Laboratory for Transport at Nanoscale Interfaces/ Empa-Swiss Federal Laboratories for Materials Sci, Switzerland; 2Institute for Building Materials/ETH Zürich-Swiss Federal Institute of Technology, Switzerland; 3Laboratory for Transport at Nanoscale Interfaces/Empa - Swiss Federal Laboratories for Materials Sci, Switzerland

Wood is a fiber-reinforced, orthotropic composite material, which shows complex anisotropic optical characteristics induced by the preferential orientation of the cellulose microfibrils in the THz domain. We hypothesize that in addition to their birefringent properties the helical arrangement of microfibrils could also exhibit optical activity. This would allow determining microfibril angles in wood, a key feature for its mechanical properties. We propose to detect optical activity and birefringence independently using THz time-domain spectroscopy (THz-TDS) despite interference with annual ring structure. Our procedure is based on the Jones calculus formalism. In this report, we demonstrate the ability to detect left- and right-handed chirality of prototype helical structures made of copper wires and birefringence of spruce wood.

17:45 Tu-PM2-2-5
Industrial Applications With Semiconductor-Based CW Terahertz System
Eui Su Lee; Mugeon Kim; Dong Woo Park; Kiwon Moon; Il-Min Lee; Hyun-Soo Kim; Dong Hun Lee; Kyung Hyun Park
ETRI, Republic of Korea

In developing terahertz (THz) technologies that are more suitable for industrial applications, we have focused on research on continuous-wave (CW) THz technologies to develop small, low-cost, and multifunctional THz devices and systems. In this study, we present an example of a practical industrial application of our CW THz system, a nondestructive evaluation (NDE) system: cost-effective high-speed 1-D/2-D reflective imaging system and real-time thickness monitoring system of slurry film. Although further improvements to photonics-based THz technologies are necessary, we believe that efforts in this field will begin an era of THz technologies as a widely-used industrial technique.

18:00 Tu-PM2-2-6
Inspection Of Oils, Caffeine Containing Foods And Consumable Plant Leaves By Time-domain THz Spectroscopy
Mindaugas Karaliūnas1; Ignas Dapsys2; Andrzej Urbanowicz1; Gytis Vektaris3; Ausra Vektarienė3; Dalia Brazinskienė1; Svajus Asadauskas1; Irmantas Kasalynas1; Gintaras Valusis1
1Center for Physical Sciences and Technology, Lithuania; 2Department of Mathematical Modeling, Vilnius Gediminas Technical University, Department of Mathematical Modeling, Lithuania; 3Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania

Terahertz (THz) spectroscopy is a very promising and practical method for rapid and reliable food quality inspection. However, the issues related to water absorption, scattering of the medium and unambiguous detection of extremely small concentration of contaminants need to be overcome. This work show the capabilities of THz time domain spectroscopy to identify the contaminated and adulterated foods. The performance of this technique is studied on edible oils, caffeine containing foods and consumable plant leaves.

16:30 - 18:15 Tu-PM2-3 THz Devices 2

Chairperson: Iwao Hosako Room 162

16:30 Tu-PM2-3-1

Terahertz Beam Steering Based On Luneburg Lens
Kazuto Sato; Yasuaki Monnai
Keio University, Japan

A novel method of terahertz beam steering using a Luneburg lens is proposed. Based on the nature of the transverse electric wave propagation between parallel plates, we design a Luneburg lens operating around 300 GHz. We experimentally demonstrate the generation of a directional beam from the lens into free-space. We also show that the beam deflection can be changed by tilting the lower plate of the parallel plates.

17:00 Tu-PM2-3-2
Dielectric-Grating In-Lens Polarizer For Beyond 5G Communications
Marta Arias Campo1; Giorgio Carluccio2; Darwin Blanco3; Simona Bruni4; Oliver Litschke4; Nuria Llombart1
1Delft University of Technology, Netherlands; 2NXP Semiconductors, Netherlands; 3Ericsson AB, Sweden; 4IMST GmbH, Germany

A high-gain broadband leaky-wave fed lens antenna with an integrated dielectric gratings polarizer covering the whole G-band (140-220GHz) is presented. This work focuses on the polarizer gratings manufacturing and in particular on the selection of plastic materials and the fabrication process refinement. The polarizer geometry has been designed and optimized to be compatible with standard milling techniques. A quasi-analytical method based on an analysis of the lens antenna in reception is used to validate the in-lens polarizer performance. Several prototypes have been fabricated, finally obtaining an excellent match between measurements and quasi-analytical results.

17:15 Tu-PM2-3-3
Low-loss Planar Porous Components For Terahertz Beamforming
Hichem Guerboukha1; Kathirvel Nallappan1; Yang Cao1; Mohamed Seghilani2; Jose Azana2; Maksim Skorobogatiy1
1Polytechnique Montreal, Canada; 2INRS-EMT, Canada

We develop planar porous components to solve the loss problem of conventional convex optics. We show that by introducing deeply subwavelength pores in a dielectric substrate, we can fabricate a porous lens and an OAM phase plate with lower loss than their all-solid counterparts.

17:30 Tu-PM2-3-4
Characterization Of A Terahertz Isolator Using A 1.5 Port Vector Spectrometer
Fahd Rushd Faridi; Sascha Preu
Technische Universität Darmstadt, Germany

The 1.5 port vector spectrometer combines both transmission and reflection geometry of terahertz time domain spectroscopy (THz TDS) in a single setup. Here we demonstrate its capability for characterizing a non-time invariant device - a terahertz isolator, in terms of isolation level and insertion loss.

17:45 Tu-PM2-3-5
Quasi-Analytical Description Of A Double Slit Planar Dielectric Waveguide As Broadband Dispersion Compensating Element
Mario Méndez Aller; Sascha Preu
Technische Universität Darmstadt, Germany

We demonstrate dispersion compensation of dielectric waveguides by a double slit dielectric structure by a quasi-analytical solution. The concept is then confirmed with a full-wave numerical simulation of realistic rectangular waveguides.

18:00 Tu-PM2-3-6
Device For Broadband THz Spectroscopy Of 1-nL-volume Samples
Sergey Mitryukovskiy; Mélanie Lavancier; Flavie Braud; Théo Hannotte; Emmanuel Dubois; Jean-François Lampin; Romain Peretti
IEMN CNRS/Université de Lille, France

We report on our recent progress in the development of a device for light-matter interaction enhancement in the full terahertz range for precise spectroscopy of minor-volume samples. The efficient confinement of a broadband terahertz pulse to a few-nL-volume was achieved, opening new perspectives for chemical and biological applications. We discuss modifications in the fabrication process leading to the improvement of our technique, following the detailed characterization of the device performances.

16:30 - 18:15 Tu-PM2-4 Biology / Medicine 1

Chairperson: Emma MacPherson Room 269

16:30 Tu-PM2-4-1
Genomic Mechanisms Of THz-Induced Cancer Dysregulation In Human Skin
Cameron Hough1; David Purschke1; Chenxi Huang1; Lyubov Titova2; Olga Kovalchuk3; Brad Warkentin1; Frank Hegmann1
1University of Alberta, Canada; 2Worcester Polytechnic Institute, United States; 3University of Lethbridge, Canada

Intense pulses of THz radiation significantly alter gene expression and dysregulate phenotypic endpoints of cancer-related signaling pathways, including activation of an inflammatory response and suppression of pro-mitotic signaling in human skin. Of 1681 potential candidates, the predicted cancer-related dysregulation is nearly entirely localized to a subset of only 42 key driver genes belonging to 7 gene families/superfamilies. The individual and concerted regulatory roles of these genes within the relevant cancer-related pathways are elucidated and discussed in the context of gene-specific response to THz exposure and potential for clinical application.

17:00 Tu-PM2-4-2
Do Humans "shine" In The Sub THz?

Yuri Feldman1; Ksenia Baksheeva2; Roman Ozhegov2; Gregory Goltsman2; Nikolay Kinev3; Valery Koshelets3; Anna Kochnev1; Noa Betzalel1; Alexander Puzenko1; Paul Ben Ishai4
1The Hebrew University of Jerusalem, Israel; 2Moscow State University of Education, Russian Federation; 3Kotel'nikov Institute of Radio Engineering and Electronics of RAS, Russian Federation; 4Ariel University, Department of Physics, Israel

Radiometry experiments, performed on human subjects, show that in the vicinity of a central frequency 507 GHz the emission of the human skin is substantially non-equilibrium in its nature. The intensity of the radiation registered using a superconducting integrated receiver (SIR) [1], was correlated with the level of the physical and mental stress of subject under examination. This result suggests that human skin may generate sub-THz waves.

17:15 Tu-PM2-4-3
The Study Of The Optical Properties Of Serous And Mucous Tissues Of The Human Stomach

Roman Grigorev1; Anna Kuzikova1; Anna Kurasova1; Petr Demchenko1; Artyom Senyuk2; Abdo Khamid2; Mikhail Khodzitsky1
1ITMO University, Russian Federation; 2Pavlova First St. Petersburg State Medical University, Russian Federation

The optical properties of mucous and serous fresh tissues of stomach were obtained using the method THz time-domain spectroscopy in the reflection mode. The difference in the optical properties of the two types of stomach tissue can be explained by their different morphology. The data may be used for intraoperative and endoscopic diagnostics of cancer.

17:30 Tu-PM2-4-4
Measurements Of Effective Porosity Of Pharmaceutical Tablets Using THz TDS

Iliya Tikhomirov1; Daniel Markl2; Mira Naftaly1
1National Physical Laboratory, United Kingdom; 2Strathclyde University, United Kingdom

The pharmaceutical industry requires a rapid nondestructive technique for monitoring porosity of tablets. Here porosity of compressed lactose pellets was investigated using THz time-domain spectroscopy (THz TDS) with the aid of index-matching medium.

17:45 Tu-PM2-4-5
Quasi-one-dimensional Terahertz Phononic Band Gap In Phospholipid Tails

Kaicheng Wang1; Jingchao Tang1; Jialu Ma1; Lianghao Guo1; Yang Yang1; Wenfei Bo1; Zhe Wu1; Zhao Wang1; Haibo Jiang2; Baoqing Zeng1; Yubin Gong1
1University of Electronic Science and Technology of China, China; 2Chengdu Institute of Biology, Chinese Academy of Sciences, China

Terahertz vibrational modes and quasi-one-dimensional terahertz phononic band gap in hydrocarbon tails of phospholipids are revealed through vibration calculation based on the ab initio density functional theory (DFT). We get the correlation between vibrational modes and frequencies. The phononic band gap in linear hydrocarbon chains provides a perspective in the interpretation of biochemical phenomena related to biological membranes, such as the photosynthetic energy transfer pathway and the electron transport chain in the inner mitochondrial membrane.

18:00 Tu-PM2-4-6
Non-Destructive Characterization Of Pharmaceutical Tablets Using Terahertz Frequency Domain Spectroscopy
Anis MoradiKouchi1; Marin Lindsjö2; Jan Stake1; Staffan Folestad2; Helena Rodilla1
1Chalmers University of Technology, Sweden; 2AstraZeneca, Sweden

In this paper, terahertz frequency domain spectroscopy (THz-FDS) technique has been employed to study the impact of porosity in tablets on their optical constants, such as the effective permittivity. Four sets of training tablets with different percentage of active ingredient and compaction force were generated with microcrystalline cellulose (MCC) as the excipient and indomethacin as the active pharmaceutical ingredient. The results show that the extracted effective permittivity is sensitive to the change of porosity in tablets and it is unique for different concentration of indomethacin. Therefore, THz-FDS technique has been revealed to be a promising tool in the quality inspection of pharmaceutical tablets.

16:30 - 18:15 Tu-PM2-5 Materials 2

Chairperson: Patrick Mounaix Room 101

16:30 Tu-PM2-5-1
Can We Observe Vibrational Confinement In Lyophilised Proteins Using Terahertz Spectroscopy?
Talia Shmool; J. Axel Zeitler; Markus Leutzsch; Michael D. Mantle
Department of Chemical Engineering and Biotechnology, University of Cambridge, United Kingdom

Abstract-The purpose of this work was to use terahertz time-domain spectroscopy (THz-TDS) to investigate the vibrational dynamics of freeze-dried protein formulations and the behaviour of these materials below and above the glass transition temperature. In contrast to small organic molecules and polymers which exhibit continuously increasing absorption with temperature, a number of lyophilised formulations examined in this work show a plateau of absorption above 300 K. This plateau suggests that at high temperatures the protein molecules are confined in the surrounding excipient matrix. This vibrational confinement in the solid-state is uniquely observed using THz-TDS, and this work could provide insight into predicting formulation stability.

16:45 Tu-PM2-5-2
Broadband Spectroscopy Of Materials With An Integrated Comb-Based Millimeter-Wave Detector
Babak Jamali; Jiashu Zhou; Aydin Babakhani
University of California, Los Angeles, United States

A miniaturized broadband spectroscopic sensor using a fully integrated millimeter-wave detector is presented. The detector chip generates a frequency comb with a tunable spacing as a reference to downconvert received signals. By tuning the comb spacing, the detector can detect frequency tones from 50 GHz to 155 GHz with a resolution only limited to the line width. A spectroscopy setup including the detector and four sheets made of different materials is implemented to characterize the frequency response of materials in this frequency range.

17:00 Tu-PM2-5-3
THz Absorption And Refraction Of KTA Crystal At Low Temperatures

Zhiming Huang1; Jingguo Huang1; Yanqing Gao1; Gaofang Li1; Yury Andreev2; Grigory Lanskii2; Valery Losev3
1Shanghai Institute of Technical Physycs, China; 2Institute of Monitoring of Climatic and Ecological Systems SB RAS, Russian Federation; 3Institute of High Current Electronics SB RAS, Russian Federation

There is a significant interest to determine potential of widely used UV - near IR nonlinear crystals for frequency conversion into the THz range. Potassium titanyl arsenate KTiOAsO4 (KTA) is one of them. Main its advantage in comparison with the other oxide nonlinear crystals such as LBO, BBO or KTP, is significantly higher second-order (d33=16.2 pm/V at 1.064 micronmeter in the mid-IR) nonlinear susceptibility and long (5.3 micronmeter at zero transmittance level) mid-IR cutoff wavelength. As for comparison with semiconductor nonlinear crystals, KTA crystal possesses muchhigher damage threshold. Refractive indices of KTA crystal at THz region were measured before only at room temperature. Here cryogenic THz spectrometer is designed with precision temperature control. Optical properties of KTA crystal (absorption coefficients and refractive indices) are investigated in detail with THz-TDS in the temperature range 5-300 K. Refractive indices can be approximated in the form of dispersion equations for different

17:15 Tu-PM2-5-4
Mechanism Between Material Microstructures And Terahertz Dielectric Properties

Bin Yang
University of Chester, United Kingdom

Significant progress has been made in developing reliable Terahertz (THz) measurement spectroscopy to extract materials' dielectric properties, however, systematic research on exploring intrinsic mechanism between microstructure of ceramics and THz dielectric properties such as loss, permittivity and dispersive characters has barely started. The paper focuses on one dielectric ceramic system (TiO2), its addition with Zn2SiO4 dielectrics and one hexa-ferromagnetic system to expatiate the association.

17:30 Tu-PM2-5-5
Time-resolved THz Spectroscopy Of Conducting Polymers

Jérôme Degert; Frédéric Dutin; Marc Tondusson; Eric Freysz
Université de Bordeaux - LOMA, France

We study, by terahertz time-domain and optical pump-THz probe spectroscopies, the optical and electrical properties of the PEDOT/PSTFSIK polymer. The latter is designed to get reed of some drawbacks of the well-known and widely used conducting polymer: the PEDOT/PSS. The optoelectronic properties in the THz range of both compounds are compared, as well as the relaxation mechanisms taking place after their photoexcitation by ultrashort optical pulses.

17:45 Tu-PM2-5-6
Dynamics Of Hydrogen Bonds And Cross-linked Structures In Polyurethane film Observed By Terahertz Spectroscopy

Hiromichi Hoshina1; Yuichi Saito2; Takumi Furuhashi3; Tomomi Shimazaki3; Manabu Sawada3; Yasunori Hioki3; Chiko Otani1
1RIKEN Center for Advanced Photonics, Japan; 2RIKEN, Japan; 3Murata Manufacturing Co., Ltd., Japan

Terahertz (THz) absorption spectra of the cross-linked polyurethane films are observed at the temperature between 30-180 °C. The obtained spectra show characteristic absorption band at 3 THz assigned as hydrogen bonded urethane group. Another band at 7 THz was assigned as intermolecular vibration of cross-linked structures between polymer chains. The temperature dependent spectra were analyzed by the perturbation correlation moving window two-dimensional spectroscopy (PCMW2D) to clarify the slight spectral change. The thermal behavior of the absorption intensities shows the dynamics of hydrogen bonds and cross-linked structures in the polyurethane films.

18:00 Tu-PM2-5-7
Temperature Dependent Giant Birefringence And Dichroism Of A BiFeO3 Single Crystal In The Terahertz Frequency

Zuanming Jin1; Yuqing Fang1; Xiumei Liu2; Jiajia Guo2; Yan Peng1; Yiming Zhu1; Zhenxiang Cheng3; Guohong Ma2
1Shanghai Key Lab of Modern Optical System, and Engineering Research Center of Optical Instrument and, China; 2Shanghai University, China; 3University of Wollongong, Australia

THz time-domain spectroscopy (THz-TDS) is used to study the THz-optical properties of a single crystal bismuth ferrite (BiFeO3). The anisotropy of BiFeO3 is strongly dependent on the temperature. A giant birefringence is observed up to around 3.6.

18:30 Tu-PM2-5-8
Competing Interplay Of Photo-thermal And Photo-doping Effect During Light-induced Ultrafast Insulator-to-Metal Transition In VO2 Nanofilms At Terahertz Frequency
Zhaohui Zhai1; Liang-Hui Du1; Si-Chao Chen2; Li-Guo Zhu1
1Institute of Fluid Physics, China Academy of Engineering Physics, China; 2Department of Optics and Optical Engineering, University of Science and Technology of China, China

The competing interplay of photo-thermal and photo-doping effect of VO2 nanofilm under fs laser excitation was studied at terahertz frequency. We find that with photo-thermal effect generated by fs laser pulses, both the character time constant of insulator-to-metal phase transition and the pump fluence threshold of transition were decreased, while the amplitudes of the two photo-response are competing.

16:30 - 18:15 Tu-PM2-6 Metamarials 3

Chairperson: Yiming Zhu Room 151

16:30 Tu-PM2-6-1
THz Resonances With Infinite Lifetime In Array Of Gold Resonators
Niels van Hoof1; Stan ter Huurne1; Diego Abujetas2; José Sanchez-gil2; Jaime Gómez Rivas1
1Eindhoven University of Technology, Netherlands; 2Instituto de Estructura de la Materia Consejo Superior de Investigaciones Científicas, Spain

Metasurfaces consisting of two resonators per unitcell can support resonances with infinitely long lifetime known as bound states in the continuum. We investigate theoretically and experimentally the conditions leading to the formation of these resonances in gold particle arrays.

17:00 Tu-PM2-6-2
Broadband Terahertz Quarter-Wave Plate Design

Xiaolong You; Christophe Fumeaux; Withawat Withayachumnankul
The University of Adelaide, Australia

A broadband terahertz quarter-wave plate design based on an extended analytical approach has been presented and numerically demonstrated. The simulations reveal that this quarter-wave plate enables a linear-to-circular polarization conversion with a 3-dB axial ratio of 53.3%, ranging from 205 to 354 GHz. It is worth of noting that this presented approach has a potential to realize broadband transmissive metasurfaces for other wavefront and phase control functionalities, such as beam focusing, beam deflection, and polarization rotation.

17:15 Tu-PM2-6-3
Broadband And Wide—Angle Terahertz Reflective Half—Wave Mirror
Rajour Tanyi Ako1; Wendy S. L. Lee2; Madhu Bhaskaran3; Sharath Sriram3; Withawat Withayachumnankul2
1Functional Materials and Microsystems Research Group and the Micro Nano Research Facility, RMIT Univ, Australia; 2Terahertz Engineering Laboratory, School of Electrical and Electronic Engineering, The University of Adelaide, Australia; 3Functional Materials and Microsystems Research Group and the Micro Nano Research Facility, RMIT University, Australia

Linear—to—linear polarization conversion of electromagnetic wave has application in various fields including communications, imaging, and sensing. Available polarization-control devices enabled by metasurfaces are limited in bandwidth, efficiency and acceptance angle. Herein, a reflective half—wave mirror composed of T—shaped resonators is proposed and experimentally evaluated. Measured results show a bandwidth of 95% and 100% around a center frequency of 0.7 THz for the normal and 45° angle of incidence. The measured results agree well with the simulation. An average polarization conversion ratio (PCR) greater than 80% is observed across 0° to 45° incidence angles.

17:30 Tu-PM2-6-4
Femtosecond Laser Processing And Evaluation Of Broadband THz Anti-Reflection Structures

Haruyuki Sakurai; Natsuki Nemoto; Kuniaki Konishi; Ryota Takaku; Yuki Sakurai; Nobuhiko Katayama; Tomotake Matsumura; Junji Yumoto; Makoto Kuwata-Gonokami
The University of Tokyo, Japan

We fabricate terahertz anti-reflection structures on the surface of high-resistivity silicon via femtosecond laser processing, demonstrating broadband increase in transmissivity over 0.3 - 2.5 THz, and investigate the spectral characteristics by using numerical simulation. We successfully reproduce the observed result, and attribute transmittance drop-off in the higher frequency region to increasing material loss, not structural effects, induced by the laser-ablation fabrication process.

17:45 Tu-PM2-6-5
Free-standing Meta-surface On Ultrathin Si Substrate For High-transmission Phase Shifts In The 3.0-THz Band

Shohei Hayashi1; Takehito Suzuki2; Kazunori Tanaka1; Kazuki Horita1; Hiroyasu Fujiwara1; Kazuue Fujita1
1Hamamatsu Photonics K.K., Japan; 2Tokyo University of Agriculture and Technology, Japan

We present a free-standing meta-surface for a high-transmission phase shift in the 3.0-THz band. The structure consists of subwavelength Au patterns with 278,273 units of meta-atoms on both the front and back of an ultrathin (4 µm thick) silicon substrate. The meta-surface for the low terahertz range has been fabricated by etching on a flexible polymer substrate with metal layers. High-precision fabrication of the meta-surface on a silicon substrate by semiconductor processing techniques is powerful and essential for the integration with terahertz semiconductor sources. Measurements by terahertz time-domain spectroscopy (THz-TDS) demonstrate a high transmission of 0.91 and a phase modulation of -0.86π at 2.8 THz agreeing well with simulations. The meta-surface in the high terahertz range can be applied in an ultrathin meta-lens for terahertz quantum cascade laser sources.

18:00 Tu-PM2-6-6
Broadband Terahertz Quarter-wave Plates Via Multipolar-interference-assisted All-dielectric Metamaterials

Da-Cheng Wang; Song Sun; Zheng Feng; Wei Tan
Microsystem and Terahertz Research Center, China

All-dielectric metamaterials with multipolar Mie resonances are proposed and experimentally realized, which operate as a broadband terahertz quarter-wave plate. Composed of elliptically-shaped silicon pillar arrays, the proposed metamaterials support dipole and quadrupole resonance modes. The constructive and destructive interferences among these modes could minimize reflection and maximize transmission. Both numerical and experimental results of the meta-device reveal close to unity transmission and 270 degrees phase delay between two orthogonal directions in a broadband, making the meta-device operate as a terahertz quarter-wave plate. Such multipolar-interference-assisted all-dielectric metamaterials promise a new paradigm for broadband low-loss terahertz devices.

18:15-19:30 - Poster session - Tu-Po 2 - Room 8

Enhanced Terahertz Emission Bandwidth From Photo-conductive Antenna With Embedded Plasmonic Nano-pillar Array
Arkabrata Bhattacharya; Dipa Ghindani; S. S. Prabhu
Tata Institute of Fundamental Research, India

In this work, we demonstrate a novel photo-conductive antenna (PCA) design, capable of emitting Terahertz radiation with enhanced bandwidth. This device consists of Au electrodes on semi-insulating GaAs substrate. A plasmonic nano-structure array is embedded in the substrate between the two electrodes. The role of this array is two-fold. The plasmonic enhancement of the 800 nm IR light near the nano-structures serves as a rich source of photo-generated charge carriers which are accelerated to generate the THz radiation. Secondly, the nano-structures acts as defect sites which enables fast carrier relaxations, hence, effectively enhancing THz bandwidths. At the same time the terminal currents are highly reduced implying robustness of the device to high applied bias voltages.

0.4 MW Terahertz Power Generation Through Bias-Free, Telecommunication-Compatible, Photoconductive Nano-Antennas

Deniz Turan; Nezih Tolga Yardimci;
Mona Jarrahi
University of California, Los Angeles, United States

We present a bias-free, telecommunication-compatible, photoconductive terahertz source that generates terahertz powers as high as 0.4 mW, enabling time domain terahertz spectroscopy with up to 90 dB dynamic range over a 3.5 THz bandwidth.

Towards Bandwidth-enhanced GaN-based Terahertz Photoconductive Antennas

Dipa Ghindani1; Arkabrata Bhattacharya2; Sumayya Samad3; Amit Shah4; Arnab Bhattacharya4; Shriganesh Prabhu5
1Tata Institute of Fundamental Research, India; 2Tata Institute of Fundamental Research, Foton Lab, India; 3International School of Photonics, Cochin University of Science and Technology, CUSAT, India; 4Tata Institute of Fundamental Research, India; 5Tata Institute of Fundamental Research, Foton Lab, India

In this work, we explore a photoconductive antenna for the emission of Terahertz radiation based on Gallium Nitride (GaN) epilayers. Typically, GaN has faster carrier relaxation times as compared to SI-GaAs, which is conventionally used as substrate for conventional photoconductive antennas. Faster carrier lifetime is expected to result into enhanced bandwidth of the emitted THz radiation.

THz TDS System Driven By A Commercially Available Laser Diode

Jan Balzer1; Sebastian Tonder1; Jannik Lehr2; Martin Koch2
1University Duisburg-Essen, Germany; 2Philipps University Marburg, Germany

We use a commercially available laser diode to drive a standard THz TDS system. The dispersion of the laser diode is compensated by a standard single mode fiber which leads to a pulse duration below 800 fs. The measured THz traces show frequency components up to 1 THz.

Effect Of Femtosecond Laser Polarization On Terahertz Emission From Cluster Nanoplasma

Nikolay Kuzechkin1; Alexei Balakin1; Murat Dzhidzhoev1; Vyacheslav Gordienko1; Igor Ivanov1; Timur Semenov2; Alexander Shkurinov1
1Lomonosov Moscow State University, Russian Federation; 2FSRC "Crystallography and Photonics" RAS, Russian Federation

We present the results of experimental studies of THz emission from argon cluster nanoplasma switched by the intense femtosecond laser pulses. We have performed measurements of the angular distribution of the THz radiation emitted from the clustered nanoplasma with two polarization states of the linearly polarized laser beam. We have found that polarization state of the laser radiation may influence on the efficiency of THz generation in cluster beam.

Direct Comparison Of PIN And UTC Photodiodes For Continuous-Wave Terahertz Emission

Simon Nellen1; Tadao Ishibashi2; Lauri Maximilian Schwenson1; Robert B. Kohlhaas1; Lars Liebermeister1; Steffen Breuer1; Anselm Deninger3; Martin Schell1; Bjoern Globisch1
1Fraunhofer HHI, Germany; 2NTT Electronics Techno Corporation, Japan; 3TOPTICA Photonics AG, Germany

We provide the first-ever direct comparison of the terahertz (THz) output of fiber-coupled UTC- and PIN-based continuous-wave emitters. As both emitters are characterized in the same setup, the observed differences can be traced back to the diode structure itself. We find large differences for frequencies below 350 GHz, where each device excels in a certain spectral range. Between 350 GHz and 1 THz, both emitters achieve a comparable THz output.

Combined UTC-PD Integrated THz Source And A Leaky Wave Antenna With Complementary Split Ring Resonators Along A Planar Goubau Line

Tahsin Akalin1; Abdallah Chahadih2; Ibrahim Türer3; Miguel Navarro-Cía4; Miguel Beruete5; Abbas Ghaddar2
1Lille University, France; 2Lebanese University, Faculty of Science, section V, Lebanon; 3Airbus Defence and Space, Germany; 4University of Birmingham, School of Physics and Astronomy, United Kingdom; 5Universidad Pública de Navarra UPNA, Spain

We have fabricated a terahertz source based on the combination of an integrated Uni-Travelling-Carrier Photodiode (UTC-PD) and a leaky wave antenna. The UTC-PD is a broadband source and we have used an efficient transition from CPW to Planar Goubau Line (PGL). In this PGL section, we have included complementary Split Ring Resonators (c-SRR) in order to obtain a leaky wave antenna (LWA). The broadband behavior of the source and of the transition allow us to design systems at a given frequency range by modifying only the c-SRR along the PGL.

Different Plasmonic Regimes Of Laser-Plasma Terahertz Generation

Vasily Kostin1; Irina Osovitskaya1; Nikolay Vvedenskii2
1University of Nizhny Novgorod, Russian Federation; 2Institute of Applied Physics, Russian Academy of Sciences, Russian Federation

The laser-plasma terahertz generation by one-color ultrashort ionizing pulses is studied using new model allowing the motion of the plasma electrons under forces both linear and quadratic in ionizing optical field. We determine different regimes of generation (with different plasmonic modes excited) and describe how the duration and phase structure of the ionizing pulse can affect not only the terahertz energy, but also the terahertz spectrum due to plasmonic effects.

A Cavity-coupled Microbolometer Terahertz Detector With A Metamaterial Reflector

Xuecou Tu; Peng Xiao; Zhihao Shao; Chengtao Jiang; Yaqian Wu; Xiaoqing Jia; Lin Kang; Jian Chen; Peiheng Wu
Nanjing University, China

In summary, we demonstrated a tunable Nb5N6 microbolometer with a movable MM reflector for THz detection. Continuous tuning over the free spectral range was achieved. The control of polarization is expected to aid the future implementation of our Nb5N6 microbolometers with broadband metamaterial polarizing reflector tuner structures. In addition, this type of structure has a good prospect in the large array of terahertz devices because of its easy integration and advantage in device packaging.

Possible Phonon-induced Electronic Bi-stability In VO2 For Ultrafast Memory At Room Temperature

Yong Tan1; Hang Zhao1; Liangliang Zhang2; Mostafa Shalaby2; Weber Cedric3; Yan Zhang2; Cunlin Zhang2; Acharya Swagata3; Cunningham Brian4; Gruning Myrta4; Kai Liu5; Mark Schilfgaarde3
1Beijing Institute of Technology, China; 2Capital Normal University, China; 3King's College London, United Kingdom; 4School of Mathematics and Physics, Queen's University Belfast, United Kingdom; 5Tsinghua University, China

This concretely addresses a long-standing controversy on the role of phonons in the transition where the M1 phase of VO2 is a band insulator with a gap that is too large for pure many-body effects to stabilize a MIT without nuclear displacements.

Terahertz Generation In Gallium Nitride Quantum Wells

Abas Roble1; Morgan Hibberd1; Menno Kappers2; Rachel Oliver2; Darren Graham1
1School of Physics and Astronomy & Phtoton Science Institute, The University of Manchester, United Kingdom; 2Department of Material Science and Metallurgy, University of Cambridge, United Kingdom

Terahertz emission spectroscopy was used to characterize InGaN/GaN and GaN/AlGaN quantum well structures grown along the polar c-axis and investigate the role of the built-in electrostatic fields in the generation of terahertz radiation. The fields were first calculated using a self-consistent k•Ã,p solver and compared to the magnitudes of the transient electric fields generated when the structures were excited in reflection geometry with femtosecond laser pulses.

Generation Of Spontaneous Parametric Down-converted Photons In The Sub-terahertz Frequency Range At 660nm

Bjoern Haase1; Mirco Kutas1; Felix Riexinger1; Patricia Bickert1; Andreas Keil1; Daniel Molter1; Michael Bortz1; Georg von Freymann2
1Fraunhofer ITWM, Germany; 2Department of Physics and Research Center OPTIMAS, Universität Kaiserslautern, Germany

There are two crucial steps towards terahertz quantum sensing. First, there is the challenge to deliver a source of entangled photons in the terahertz range. Second, measuring terahertz radiation using photons in a different spectral range has to be possible. As we generated entangled photons in the terahertz range by spontaneous parametric down conversion (SPDC), we received the first milestone. The detected signals matches both for down- and for up-conversion for forward as well as for backward terahertz radiation the calculated frequency angular spectrum both qualitative and quantitative. By observing difference frequency generation of external terahertz radiation with VIS pump photons, we achieved both steps towards terahertz quantum sensing.

Spatial And Temporal Field Evolution Of Evanescent Single-Cycle THz Pulses

Daniel Lake1; Edward Snedden2; David Walsh2; Steven Jamison1; Darren Graham3
1Lancaster University, United Kingdom; 2Accelerator Science and Technology Centre, United Kingdom; 3The University of Manchester, The Photon Science Institute, United Kingdom

The temporal and spatial evolution of single-cycle THz pulses travelling across a dielectric boundary with effective surface velocity below c has been examined. The resulting subluminal evanescent waves in the near field vacuum region are potential drivers of particle accelerators. The electro-optic temporal and spatial imaging of the THz pulses emitted from the surface were measured in the near field, as a function of distance from the dielectric boundary, and reveal both temporal broadening and field decay that is dependent on the effective velocity of the wave in the plane of the boundary.

Lensless Infrared Image Processing Method Based On Fresnel Aperture
Dexing Liu; Jiaxin Shi; Yunkui Zhang; Ming Cai; Qingchen Niu; Guanhao Cui; Jun Gou; Jun Wang
University of Electronic Science and Technology of China, China

In this paper, the fringe phase scanning method based on Moire fringe is used to reconstruct the phase information of the target object. And we developed the two algorithms which are named as primary reconstruction and secondary reconstruction for different requirements. Combined with image enhancement technology, we can realize the lensless infrared imaging. This method is also beneficial to the miniaturization and integration of infrared focal plane detectors.

Low-pump Irradiance To Modulate THz Waves Driven By Photo-generated Carriers In An InAs Slab

Eduardo Alvear1; Stephane Blin2; Philippe Nouvel2; Fernando Gonzalez-Posada2; Rafik Smaali3; Roland Teissier2; Alexei Baranov2; Thierry Taliercio2; Emmanuel Centeno3
1Univ. Clermont Auvergne, France; 2IES, France; 3Univ. Clermont Auvergne, France

We theoretically and experimentally study the THz electromagnetic properties of an undoped-InAs slab whose permittivity is optically modified by a photo-generation process. The modulation of the permittivity is calculated by solving the ambipolar rate equation for the free carriers. Experiment results demonstrate that InAs is a promising semiconductor to manufacture fast and efficiently on-chip THz components. We show a high modulation of the THz transmission up to 100% from 0.75 to 1.1THz at very low pump fluence in the continuous wave regime. We also demonstrate a high-speed transmission modulation rate up to the MHz range with a modulated pump.

High Speed Antenna Enhanced Mid-infrared Quantum Cascade Detector

Gregory Quinchard1; Alexandre Larrue1; Alexandre Delga1; Michel Garcia1; Colin Mismer1; Virginie Trinité1; Axel Evirgen1; Michael Hakl2; Jean-François Lampin2; Emilien Peytavit2; Stefano Barbieri2
1III-VLab, France; 2IEMN, France

We demonstrate a λ =10.3 µm Quantum Cascade Detector embedded in a subwavelength optical patch antenna cavity. In this structure, the responsivity is enhanced by the microcavity effect and the dark current is reduced thanks to the antenna effect. The system is used as photo-mixer in a coherent photodetection scheme. It opens the way for high sensitivity and high-speed operation and brings new perspectives for room-temperature photodetection.

TeraHertz Generation in Semiconductor Microcavities

Hadrien Vergnet1; Simon Huppert1; Robson Ferreira1; Aristide Lemaître2; Jacqueline Bloch2; Sukhdeep Dhillon1; Emmanuel Baudin1; Jérôme Tignon1
1Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Universit, France; 2Centre de Nanosciences et de Nanotechnologies (C2N), CNRS - Université Paris-Sud / Paris-Saclay, France

We explore the potential of engineered exciton-polaritons in monolithic microcavities as compact and tunable THz emitters, by simultaneous THz and NIR spectroscopy

Numerical Study Of CO Laser Down-conversion In ZnGeP2 Crystal to THz Range
Igor Kinyaevskiy1; Andrey Ionin1; Yury Klimachev1; Yury Andreev2
1P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Russian Federation; 2Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of Russian Academy, Russian Federation

Difference frequency generation of rotational-vibrational lines of nonselective CO laser in ZnGeP2 crystal was numerically studied. It was shown that the difference frequency spectrum can be tuned at least in the wavelength range of 70--1300 ÃfŽÃ,¼m. The conversion efficiency can be up to 10-2%.

Room Temperature Silicon Detector For IR Range Coated With Ag2S Quantum Dots
Ivan Tretyakov1; Alexander Shurakov1; Alexey Perepelitsa1; Natalya Kaurova1; Tatyana Zilberley2; Sergey Ryabchun1; Mikhail Smirnov3; Oleg Ovchinnikov3; Gregory Goltsman1
1MSPU, Russian Federation; 2Moscow Institute of Physics and technology, Russian Federation; 3VSU, Russian Federation

For decades silicon has been the chief technological semiconducting material of modern microelectronics and has had a strong influence on all aspects of society. Applications of Si-based optoelectronic devices are limited to the visible and near infrared ranges. For photons with energy less than 1.12 eV silicon is almost transparent. The expansion of the Si absorption to shorter wavelengths of the infrared range is of considerable interest to optoelectronic applications. By creating impurity states in Si it is possible to cause sub-band gap photon absorption. Here, we present an elegant and effective technology of extending the photoresponse of towards the IR range. Our approach is based on the use of Ag2S quantum dots (QDs) planted on the surface of Si to create impurity states in Si band gap. The specific sensitivity of the room temperature zero-bias Si_Ag2S detector is 1011 cmâ^sHzW-1 at 1.55μm. Given the variety of available QDs and

Polarization Control Of Terahertz Spintronic Emitter Combined With Liquid Crystal By The External Magnetic And Electric Field

Makoto Nakajima1; Hongsong Qiu1; Lei Wang2; Zhixiong Shen3; Kosaku Kato1; Yohei Koike1; Masashi Yoshimura1; Wei Hu3; Yanqing Lu3
1Osaka University, Japan; 2Nanjing University Post and Telecommunications, China; 3Nanjing University, China

We demonstrate a polarization-tunable terahertz emitter that integrates a ferromagnetic heterostructure and large birefringence liquid crystals by the external magnetic and electric field. The direction of the magnetic field can control the emitted THz wave from linear to circular polarization. The phase retardation in liquid crystal layer between ordinary and extraordinary directions is continuously adjustable by the low-voltage electric field.

Terahertz Pulse Emission From GaInAsBi
Ričardas Norkus; Sandra Stanionytė; Andzej Urbanowicz; Andrius Bičiūnas; Vaidas Pačebutas; Arūnas Krotkus
State research institute Center for Physical Sciences and Technology, Lithuania

The quaternary GaInAsBi alloy epitaxial layers were grown on InP substrates with 6% Bi. It was found that thick layers are strained and has short of the order of few picoseconds carrier lifetimes. The THz emission was investigated using GaInAsBi layer as an unbiased surface emitter and as a substrate for photoconductive antenna. It was observed that fabricated THz emitters were sensitive to the optical pulses with the wavelengths longer than 2 µm. The demonstrated spectral characteristics of THz pulses obtained when using Er-doped fiber laser for the photoexcitation were comparable with those observed in other emitters used for THz-TDS systems

Synchronous Pumping Terahertz Parametric Oscillator Driven By Amplified Picosecond Mode-locked Laser

Tomohiro Naganawa1; Heishun Zen2; Toshiteru Kii2; Hideaki Ohgaki2
1Graduate School of Energy Science, Kyoto University, Japan; 2Institute of Advanced Energy, Kyoto University, Japan

Terahertz parametric oscillator (TPO) is one of the attractive ways to generate THz waves. However this scheme has big problem because of large loss and low conversion efficiency when it is driven by a nano-second pulsed laser. In this study, we propose a novel high-conversion-efficiency TPO, which is called as synchronous pumping Terahertz parametric oscillator (sp-TPO). It uses amplified picosecond mode-locked laser pulses as a pump beam. Design and construction of the device was completed, and the first test will be performed soon. The results will be also presented at the conference.

+16 DBm High Power And High Linearity Integrated Photoreceiver For W-band Fiber Wireless Communication Applications

Toshimasa Umezawa1; Atsushi Kanno1; Atsushi Matsumoto1; Naokatsu Yamamoto1; Tetsuya Kawanishi2
1National Institute of Information and Communications Technology, Japan; 2Waseda University, Japan

We designed and fabricated an 80 GHz range high-power integrated photoreceiver operated using a zero-bias operational broadband uni-traveling carrier photodetector and a high-gain narrow-band amplifier. The results showed that by applying only a single power supply to the amplifier, the integrated photoreceiver could exhibit a higher power output at 1 dB compression (P1dB), i.e., over +16 dBm, and a 3 dB bandwidth of 6.5 GHz at 83 GHz.

High Efficient Broadband Terahertz Radiation Generated By Photoconductive Antenna Array

Wei Shi; Lei Hou; Cheng Ma; Lei Yang; Shaoqiang Wang; Chengang Dong; Hong Liu
Xi'an University of Technology, China

Coherent combination of radiations from a set of independent sources is an efficient way to obtain high power terahertz (THz) radiation. In this work, we designed and fabricated an antenna array, the THz radiations with opposite phase caused by the reverse bias electrical field existed in the conventional photoconductive antenna arrays was totally eliminated, and the synchronization of THz pulses was realized by precisely adjusting their optical paths. By these designs, we demonstrated, for the first time, the THz pulses with the combination efficiency of near 100% from photoconductive antenna array have been achieved.

Nonuniformity Study For Silicon-based BIB Terahertz Detectors

Xiaodong Wang; Yulu Chen; Bingbing Wang; Chuansheng Zhang; Haoxing Zhang
The 50th Research Institute of China Electronics Technology Group Corporation, China

In this work, Silicon-based BIB array detector has been fabricated. It is demonstrated that the minimum nonuniformity of 7.6% can be achieved. Additionally, the nonuniformities at the low bias are fundamentally less than those at the high bias, which can be attributed to the increased device temperature caused by the self-heating effect of the chip at the high bias. It can be deduced that the nonuniformity of dark current density will be out of control if the anode bias is larger than 3V due to the occurrence of avalanche randomness.

Fabrication Of Quarter THz Wavelength Resonant Cavity Using A Multiple spin Coating Process

Xing Zheng; Jingbin Wu; Yunkui Zhang; Ziji Liu; Zhiming Wu; Jun Gou; Tao Wang; Yadong Jiang
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Scien, China

Due to the long terahertz (THz) wavelength, it remains a challenging problem to achieve THz wave absorption through building an effective optical resonant cavity for THz wave with THz focal plane arrays. In this paper, a multiple spin coating (MSC) process was developed for the first time to increase the height of the optical resonant cavity. Four resonant cavities with different heights were fabricated and their abilities to absorb THz waves were tested respectively. The tests suggested that the different THz bands were absorbed effectively by the micro-bridge structure using the proposed MSC process.

Simulation Of Terahertz Spectrum Generated By Noise-like Pulse

Yu Cheng Hong1; Cheng Han Lin2; Hsiao Hua Wu2; Ci Ling Pan2
1Institute of photonics technologies, Taiwan; 2Department of Physics, Taiwan

We simulate the generation of terahertz radiation by using a photoconductive antenna excited by noise-like pulses (NLPs). Our simulation results show that the bandwidth of THz spectrum generated by NLPs is narrower than by mode-locked pulses which is from the same laser system in the low-frequency region. However, the spectrum generated by NLPs exhibits additional components extended to the higher frequency, though the power is relatively low.

High Efficient THz Time Domain Spectroscopy Using Laser Chaos

Fumiyoshi Kuwashima1; Takuya Shirao1; Kazuyuki Iwao1; Masahiko Tani2; Kazuyoshi Kurihara3; Kohji Yamamoto4; Osamu Morikawa5; Makoto Nakajima6
1Fukui Univ. of Tech., Japan; 2Research Center for Development of Far-Infrared Region, University of Fukui, Japan; 3Fac. of Educ., Univ. of Fukui, Japan; 4Research Center for Development of Far-Infrared Region, University of Fukui, Japan; 5Chair of Liberal Arts, Japan Coast Guard Academy, Japan; 6Institute of Laser engineering, Osaka Univ., Japan

Stable and wide range THz waves are obtained from the chaotically oscillated multimode-laser diode excited photoconductive antennas. This system is chap system And. this THz wave is suitable for the spectroscopy. In this paper, it is applied to distinguish water and oil.

High Sensitivity Heterodyne Electro-Optic Sampling With 1.5-µM Laser Source

Hideaki Kitahara1; Hiroyuki Kato1; Masaki Shiihara1; Akihiro Esaki1; Kohji Yamamoto1; Takashi Furuya1; Elmer Estacio2; Micheal Bakunov3; Masahiko Tani1
1University of Fukui, Japan; 2University of the Philippines Diliman, Philippines; 3University of Nizhny Novgorod, Russian Federation

A detection module for the heterodyne electro-optic sampling of terahertz pulses composed of a GaAs plate inserted into a tapered parallel plate waveguide has been designed and fabricated. The detector was installed into a standard terahertz time-domain spectrometer with a 1.5-µm femtosecond laser as a light source. The spectral bandwidth of 3.5 THz and dynamic range of 5 orders of magnitude were experimentally demonstrated, even with a photo-conductive antenna designed for 800-nm as an emitter.

Monolithic Mode-Locked Laser Diode For THz Communication

Alexandra Gerling1; Kai Tybussek2; Quentin Gaimard3; Kamel Merghem3; Abderrahim Ramdane3; Martin Hofmann1; Carsten Brenner1; Jan Balzer2
1Ruhr University Bochum, Germany; 2Universität Duisburg-Essen,Germany; 3CNRS Centre de Nanoscience et Nanotechnology, France

The need for higher data rates in wireless applications necessitates fast technological development. One option for advancement is the use of higher carrier frequencies, as this technique can incorporate previously established methods of data transfer such as modulation techniques. We show that generation and detection of multiple carrier frequencies in the THz range is possible using standard telecom equipment and a single mode-locked laser diode.

Generation Of Sub-100-kW Narrow-line Far-infrared Radiation From KTP Off-axis THz Parametric Oscillator Seeded By A Spectrally Filtered Stokes Pulse
Ming-Hsiung Wu; Wei-Che Tsai; Yu-Chung Chiu; Yen-Chieh Huang
National Tsing Hua University, Taiwan

We have reported narrow-line high-power far-infrared radiation with peak power up to 62 kW near 53 µm (~5.7 THz in units of frequency) from a pulse seeded OTPO using KTP. With 63% coupling efficiency of the silicon prism atop the KTP crystal, the measured 62-kW narrow-line far-infrared radiation in our pyrodetector correspond to 98-kW powers emitted from the KTP OTPO.

On-Chip Harmonically Mode-Locked Lasers In Generic Foundry As Frequency Multiplier For Optoelectronic Terahertz Generation
Mu-Chieh Lo; Robinson Guzmán;
Guillermo Carpintero
Universidad Carlos III de Madrid, Spain

We experimentally demonstrated optoelectronic integrated circuits which generate selectable high-order harmonics from optical frequency combs to enable terahertz generation. These two-tone sources based on mode-locked lasers monolithically integrated with frequency multipliers are developed in an InP generic foundry approach.

Development Of High-speed, Patch-antenna Intersubband Photodetectors At 10.3um

Quyang Lin1; Michael Hakl1; Stefano Pirotta2; Raffaele Colombelli2; Wenjian Wan3; Hua Li3; J. C. Cao3; Jean-Francois Lampin1; Emilien Peytavit1; Stefano Barbieri1
1Laboratoire IEMN - CNRS, France; 2Laboratoire C2N - CNRS, France; 3Key Laboratory of Terahertz Solid State Technology, Chinese Academy of Sciences, China

We present our work on the development of high-speed, GaAs-AlGaAs multi-quantum wells photodetectors at 10.3μm, based on two-dimensional arrays of patch-antenna resonators. First, the results of FDTD simulations will be presented that allowed to optimize the patch array geometry and fabricate a first generation of detectors with microwave coplanar access. Next, we will report on our initial results from dc optical characterization, namely reflectivity and photocurrent measurements.

The Gouy Phase Shift In Terahertz Time-domain Spectroscopy And Its Experimental Estimation, Modelling And Compensation

Pierre Kolejak1; Kamil Postava1; Martin Micica1; Mathias Vanwolleghem2; Jaromir Pistora1
1VSB-Technical University of Ostrava, Czech Republic; 2Université de Lille, CNRS UMR 8520, France

We propose techniques for compensation of the Gouy phase, which affects transmission time-domain spectroscopy measurements. It is proposed the method to analyze general influence of the Gouy phase. The model simulating the Gouy phase influence compared with measured data is also shown.

Single-shot Measurement Of THz Pulses With Sub-picosecond Resolution and Megahertz Acquisition Rates

Serge Bielawski1; Christophe Szwaj1; Clément Evain1; Marc Le Parquier1; Tianwei Jiang2; Cejo Lonappan2; Bahram Jalali2
1PhLAM, LIlle University, France; 2Department of Electrical and Computer Engineering, University of California, United States

We present a method allowing THz pulses to be recorded in single-shot at tens of MHz repetition rates and long record lengths, using a combination of the time-stretch data acquisition and electro-optic sampling techniques

Application Of Mosaicity Induced Disorder Controlled Rare Earth Nickelate Thin Films As THz Transmission Modulator

Gulloo LAL PRAJAPATI1; Sarmistha Das2; Dhanvir Singh Rana1
1IISER Bhopal, India; 2Physics Department, University of California, United States

Here, we have studied mosaicity induced disorder (a unique type of disorder which is transferred from substrate template to film) controlled properties of rare earth nickelate thin films. While highly oriented film exhibits sharp metal to insulator transition (MIT) and Drude type of terahertz (THz) conductivity behavior, mosaic film exhibit much more subtle and broad transition and Drude-Smith type THz conductivity behavior. On the basis of such contrasting behavior, we propose application of these films as thermally controlled THz transmission modulator: oriented film as digital modulator while mosaic film as analog modulator.

Profile Control Of One-dimensional Terahertz Moth-eye Structure Fabricated By Femtosecond Laser Processing

Xi Yu; Jongsuck Bae; Shingo Ono
Nagoya Institute of Technology, Japan

To experimentally establishing the profile dependence of antireflective characteristic of moth-eye structure at THz frequencies, one-dimensional tapered moth-eye structures were fabricated on the surface of high-resistivity silicon substrate with different aspect ratio from 1.3 to 3.2 using femtosecond laser processing. A moth-eye structure consists of Klopfentein tapers with aspect ratio of 0.7 was also successfully fabricated by adjusted the scanning pattern while femtosecond laser processing. The antireflective characteristics of these samples were evaluated experimentally by a standard terahertz time domain spectroscopy and simulated by the High Frequency Electromagnetic Field Simulation.

Application Of Laser Generated Moth-eye Structure For A Periodic Terahertz-wave Generator

Xi Yu; Shingo Ono; Jongsuck Bae
Nagoya Institute of Technology, Japan

To improve the generation efficiency of terahertz wave from periodic terahertz-wave generator, femtosecond laser was employed to fabricated moth-eye structure on the reverse of the antenna substrate (LT-GaAs). The measurement performed by a THz-TDS system showed that The AR structured antennas had a 2.5-4.4 times improvement of the output. the output signals has an overall improvement at the region of 0.1-1.5 THz. At the frequency of 0.342 THz (calculated Ãfâ? Ã¢â,¬â"¢out), 283 THz, 226 THz (experimental Ãfâ? Ã¢â,¬â"¢out of generator without and with moth-eye, the improvement are 3 times, 2.5 times, and 4.4 times, respectively.

Electromagnetic-field Analysis Of Diagonal-feedhorn Antennas For Terahertz-frequency Quantum-cascade Laser Integration

Esam Zafar1; Alexander Valavanis1; Paul Dean1; Edmund Linfield1; Giles Davies1; Yingjun Han1; Olivier Auriacombe2; Thomas Rawlings2; Brian Ellison2; Nick Brewster2; Matthew Oldfield2
1University of Leeds, United Kingdom; 2Science and Technology Facilities Council/RAL Space Department, United Kingdom

We present an electromagnetic-field analysis of a terahertz-frequency quantum-cascade laser (THz QCL) integrated with a mechanically micro-machined waveguide cavity and diagonal feedhorn. A hybrid finite-element/Fourier transform approach enables analysis of both the near-field and far-field regions and is shown to agree well with experimental observations. The far-field antenna patterns show enhancement of the beam profile when compared with an unmounted QCL, in terms of beam divergence and side-lobe suppression ratio. Furthermore, we demonstrate integration of the QCL with dual diagonal feedhorns, enabling simultaneous access to both facets of the QCL, underpinning future integration with a satellite-based receiver and frequency-stabilization subsystem

Open-Source Simulation Software For Quantum Cascade Lasers

Michael Riesch; Christian Jirauschek
Technical University of Munich, Germany

We review the state of the art in open-source simulation and optimization tools for quantum cascade lasers (QCLs) and present the mbsolve project, which is a tool for QCL dynamics simulations.

High Power THz Quantum Cascade Laser And Its Demonstration In High Resolution Holographic Imaging

Tao Jiang; Changle Shen; Zhiqiang Zhan; Ruijiao Zou; Xuemin Wang; Weidong Wu
Research Center of Laser Fusion CAEP, China

Fabrication of high power terahertz quantum cascade laser (THz QCL) based upon the resonant-phonon active region design and semi-insulating surface-plasmon waveguide with frequency at 4.4 THz and its demonstration in digital holographic imaging are presented. The maximum peak output power is 95mW at 10K in pulsed mode. The maximum working temperature is 80 K. Interestingly, by changing the injection current, the transverse mode of the laser can be switched between TM00 mode and TM01 mode. With such THz QCL as the light source, the lateral resolution of a home-built digital holographic imaging system can reach 80ÃZ¼m.

Towards A 4.75-THz Local Oscillator Based On A Terahertz Quantum-Cascade Laser With A Back-facet Mirror

Till Hagelschuer1; Heiko Richter1; Martin Wienold1; Xiang Lü2; Benjamin Röben2; Lutz Schrottke2; Klaus Biermann2; Holger T. Grahn2; Heinz-Wilhelm Hübers1
1German Aerospace Center (DLR), Germany; 2Paul-Drude Institut für Festkörperelektronik, Germany

We report on a compact terahertz (THz) source based on a quantum-cascade laser (QCL). The source is intended for a local oscillator in a THz heterodyne receiver for the detection of the fine structure line of neutral atomic oxygen (OI) at 4.7448 THz. The QCL which is mounted in a small mechanical cryocooler employs a GaAs/AlAs active-region heterostructure and a resonator with an additional back-facet mirror. This allows for low electrical pump powers of less than 1.2 W and high optical output powers of up to 8 mW. The whole setup weighs less than 4 kg. The application of such a system in a spaceborne mission appears to be feasible.

Optimization Of THz QCLs By Suppressing A Leakage Current Via High Energy States

Tsung-Tse Lin; Ke Wang; Li Wang; Hideki Hihayama
RIKEN, Japan

Terahertz quantum cascade lasers (THz QCLs) are theoretically analyzed based on the non-equilibrium Green's function (NEGF) method. Simulations reveal a carrier leakage channel from upper laser level to the first high energy state in the emitting double-well of the next period. This leakage channel is due to unintentional alignment of the two states, which is distinct from the thermally activated leakage channels. By tuning the energy of this high energy state, such leakage current is clearly suppressed.

The Material Growth, Device Fabrication And Application Of Terahertz Quantum Cascade Lasers

Weidong Wu; Xuemin Wang; Changle Shen; Tao Jiang; Zhiqiang Zhan
Research Center of Laser Fusion CAEP, China

This talk reviews our recent work on material growth, device fabrication and application of terahertz quantum cascade lasers (THz QCLs).

Advances In MOEMS-based External Cavity QCLs For Mid-IR Spectroscopy

Yuri Victorovich Flores1; Marko Haertelt1; Stefan Hugger1; Lorenz Butschek1; Christian Schilling1; Andre Merten2; Markus Schwarzenberg2; Andre Dreyhaupt2; Jan Grahmann2; Marcel Rattunde1; Ralf Ostendorf1
1Fraunhofer Institute of Applied Solid State Physics, Germany; 2Fraunhofer Institute for Photonic Microsystems, Germany

We present miniaturized MOEMS-based external-cavity (EC)-QCLs: A non-resonant, versatile version for setting arbitrary emission wavelengths or wavelength trajectories as a function of time with drive frequencies up to a few tens of Hz and a fast, resonant variant for real time (millisecond resolution) measurements. Both versions are equipped with additional cavity length control for high-resolution mid-IR spectroscopy.

High Performance Continuous-wave InP-based 2.1 ?m Superluminescent Diode With InGaAsSb Quantum Well

Jinchuan Zhang
Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Science, People's Republic of China, China

Broadband spectrum electrically pumped InP-based superluminescent diodes (SLDs) in continuous-wave (CW) are reported. The optimized active region and high quality of quantum wells are guaranteed for controlling wavelength and acquiring large mode gain. All device spectrums are centered around 2.1 μm and the full width at half maximum (FWHM) of widest spectrum is 99 nm. After the optimization of waveguide structure for higher output power, the maximum CW output power is lifted up to 30 mW. This work is of great importance to pave the way for demonstrating compact and efficient light sources based on InP material systems.

Resonant Frequency Tuning Of Terahertz Plasmonic Structures Based On Solid Immersion Method
Toshio Sugaya1; Xiangying Deng1; Yukio Kawano2
1Tokyo Institute of Technology, Japan; 2Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Institute of Techn, Japan

We report on a technique for resonant frequency tuning and miniaturization of a terahertz (THz) plasmonic structure. By applying solid immersion method to a nonconcentric plasmonic structure, we achieved resonant frequency tuning of THz plasmon and size reduction by 1/3.41 simultaneously. These results potentially lead to high-resolution THz analysis for bio-medical examination and nano-materials characterization.

Comparison Of Metallic NW And Evaporated Contact For THz Detector Modules Based On An InGaAs Schottky Diode

Ahid S. Hajo; Oktay Yilmazoglu; Suwei Lu; Franko Küppers; Thomas Kussorow
Technische Universität Darmstadt, Germany

In this paper we report a new Terahertz (THz) Schottky detector module based on vertically contacted highly doped (1 x 1018 cm-3) indium gallium arsenide (InGaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact and a standard evaporated contact (SD). These Schottky diodes were placed on a silicon lens and integrated with a pre- amplifier on a printed circuit board (PCB).

Characterization Of Uncooled Ultra Low-NEP LSMO Bolometers At 3.39 Mm And In The MWIR And LWIR Bands

Bruno Guillet1; Vanuza Marques Do Nascimento1; Victor Pierron1; Laurence Méchin1; Florent Starecki2; Carolina Adamo3; Darrell Schlom4
1GREYC - CNRS/ENSICAEN/Université de Caen Normandie, France; 2CIMAP - CNRS/ENSICAEN/CEA/Université de Caen Normandie, France; 3Cornell University, United States; 4Kavli Institute at Cornell for Nanoscale Science, United States

La0.7Sr0.3MnO3 (LSMO) uncooled suspended bolometers have been characterized at 3.39 Ã,µm (He-Ne laser) and with a blackbody source at different temperatures. These bolometers could achieve ultra low NEP values below 1 pWÃ,·Hz-1/2 with few microwatts power consumption at 300 K

A Gap Waveguide Fed Circular Polarization Antenna In The Millimeter- Wave Range

Dayan Pérez; Miguel Beruete; Iñigo Ederra
Public University of Navarra, Spain

In this paper a simple diamond-shaped slot antenna working in the millimeter-wave 5G band of 60 GHz, with circular polarization (CP), high radiation efficiency and broadband performance both in matching and axial ratio (AR) is presented. The antenna is implemented in Gap Waveguide (GW) technology, namely Ridge Gap Waveguide topology. The feeding system is a standard waveguide (WR-15) to RGW transition. The simulation results demonstrate a 14.52% reflection coefficient and AR bandwidth (|S11 < ?10 dB| and AR < 3dB) covering 59- 68 GHz (> 9 GHz) The maximum gain of the system is around 7 dB, with an efficiency close to 98%.

Investigation Of THz Tapered Parallel Plate Waveguide Integrated With A Metal Slit Array

Dejun Liu1; Borwen You1; Ja-Yu Lu2; Toshiaki Hattori1
1University of Tsukuba, Japan; 2National Cheng Kung University, Taiwan

A metal slit array in a tapered parallel plate waveguide (TPPWG) is experimentally and numerically demonstrated. The metal slit array is embedded in the center of air gaps in tapered regions, realizing multiple narrow Bragg resonances. TPPWG not only enhances the Bragg resonances but also reduces the number of non-Bragg resonances. The induced standing waves at 0.3 THz exhibits enhanced localized field with four antinodes, which originates from the interference between two THz waves divided by the metal slit array.

Design Of A Compact Cylindrical Micro-lens For Efficient Out-coupling And Collimation Of THz Radiation From A Photoconductive Antenna

Thomas Søndergaard; Christian Sørensen; Esben Skovsen
Aalborg University, Department of Materials and Production, Denmark

A compact cylindrical micro-lens is designed for efficient out-coupling and collimation of THz radiation from a photoconductive THz antenna placed on the backside of a semiconductor substrate. The full radiation pattern of the 3D lens-antenna system is calculated rigorously by using the Green's Function Volume Integral Equation Method in a form that exploits cylindrical symmetry. The lens is designed for an optimum amount of radiation emitted in a useful range of directions relative to the total emission taking into account the Purcell effect and radiation trapped inside the semiconductor substrate

Tunable Optical Frequency Shifter For Terahertz Communicaiton System

Wei Jiang1; Shanghong Zhao2; Qinggui Tan1; Xiaojun Li1; Zhongbo Zhu1
1National Key Laboratory of Science and Technology on Space Microwave, China; 2Air Force Engineering University, China

In this paper, a tunable optical frequency shifter for Terahertz (THz) communication system is proposed and demonstrated. The scheme is based on frequency multiplication operation using dual-parallel DPMZM (dual-parallel Mach-Zehnder modulator) and Mach-Zehnder interferometer (MZI). By optimizing the sub-modulators of DPMZMs, the optical carrier suppressed single-side-band signal (SSB-OCS) with adjustable order can be used for tunable optical frequency shifter, and the MZI further suppresses high order intermodulation components. The simulated results show the suppression ratio is above 30 dB, and the maximum range of optical frequency shift is over 150 GHz. The experimental test suppression ratio is over 24 dB.

Study Of Microstrip-Based Terahertz Phase Shifter Using Liquid Crystal

Yuki Takeda1; Withawat Withayachumnanku2; Yasuaki Monnai1
1Keio University, Japan; 2The University of Adelaide, Australia

We propose a microstrip-based terahertz phase shifter using liquid crystal. Voltage-controlled phase shift can be induced by incorporating liquid crystal into the dielectric substrate of the microstrip line (MSL) to cause the refractive index change. DC bias lines running in parallel to the MSL are designed to introduce minimum RF interference. Preliminary experimental results show the proof of concept of the approach.

Rapid Prototyping Of Simple Optical Elements For The Terahertz Domain

Christian Sørensen1; Esben Skovsen2
1Aalborg University, Department of Materials and Production, Denmark; 2Aalborg University, Denmark

This work shows practical details of methodologies for conventional milling of arbitrary spherical lenses from high-density polyethylene as well as the production and polishing of off-axis parabolic mirrors using fused filament fabrication 3D printing. The techniques allow for low-volume, low-cost and fast prototyping of large optical elements for prototype setups.

THz Gratings Produced By Laser Cutting

Jan Ornik; Yingzhi Zhang; Maximilian Schneider; Mehdi Taherkhani; Hakan Alaboz; Martin Koch
Philipps-Universität Marburg, Germany

We produced terahertz gratings from aluminum and PVC foil by laser cutting. The performance of the produced gratings was simulated and found to be in good agreement with the experimental characterization.

A Quasi-optical Transmission Line For The ECR Ion Source

jianwei liu1; junwei guo2; xinjian niu1; yinghui liu1; hui wang1; guo guo1; Safi Ullah1; Abdur Rauf1; xu sun1
1University of Electronic Science and Technology of China, China; 2Institute of Modern Physics (IMP), Chinese Academy of Science, China

A compact, efficient, 45GHz/20KW quasi-optical transmission line consisting five quasi-optical mirrors for the ECR ion source, which constructed by the Institute of Modern Physics(IMP), Chinese Academy of Science has been proposed. A computer code for vector analysis of the electromagnetic fields in mirror systems has been developed in terms of the vector diffraction theory. Based on Stratton-Chu formula and mirror optimization program, the structure of the five quasi-optical mirrors has been obtained. The simulation results show that the power transmission efficiency from the output of the Matching Optical Unit( MOU) to the vacuum widow which connected with superconducting ECR ion source is 93.53%. The experimental results indicate that a good agreement between measurement and theoretical prediction is obtained.

Development Of The Planar AlGaN/GaN Bow-tie Diodes For Terahertz Detection

Justinas Jorudas; Justina Malakauskaitė; Liudvikas Subačius; Vytautas Janonis; Vytautas Jakstas; Vitalij Kovalevskij; Irmantas Kasalynas
Center for Physical Sciences and Technology, Lithuania

Completely planar bow-tie (BT) diodes for terahertz (THz) detection were developed on AlGaN/GaN high electron mobility transistor (HEMT) structures employing a shallow ion-implantation for electric isolation. Heating in a two dimensional electron gas (2DEG) layer in the apex zone of geometrically shaped semiconductor was used for THz detection. The diodes were developed with various apex widths varying from 17 µ to 500 nm. The responsivity of the sensor was found to be increasing non-linearly with the decrease of the apex width. In addition, detected signal dependence on frequency was observed with a maximum sensor response at about 150 GHz defined by a THz antenna coupling efficiency and not 2DEG heating effects. These results highlight a potential of the planar AlGaN/GaN BT diodes for the usage upper THz frequency range.

Concept Of A Prism Spectrograph For Infrared Linear Array Detectors

Ulrich Schade1; Eglof Ritter2; Ljiljana Puskar1; Paul Dumas3
1HZB, Germany; 2HUB, Germany; 3SOLEIL Synchrotron, France

We discuss the concept of an IR spectrograph suitable for linear array detection. The dispersive element of the spectrograph is based on an arrangement of commercially available low-cost prisms. The dispersion is such that the whole spectral bandwidth of interest is distributed along the linear array of detector pixels in such a way to achieve an optimum for the spectral resolution. The concept is exemplarily shown for the design of a spectrograph working in the range between 5000 and 2500 wavenumbers spread onto a linear 128-pixel array detector.

A Low-Profile Sub-Terahertz Transmit-Array Antenna With High Gain Enhancement

Zhongbo Zhu1; Weidong Hu2; Xianqi Lin3; Xiaojun Li1
1The National Key Lab. of Sience and Technology on Space Microwave, China; 2Beijing Institute of Technology, China; 3University of Electronic Science and Technology of China, China

A compact transmit-array (TA) antenna with reduced profile and improved radiation gain is proposed in this paper. The proposed transmitting surface, with a thickness of 0.127 mm (0.042 ?0 @105 GHz), is employed here to adjust the phase distribution across the aperture of a shortened feed horn. The full TA prototype is fabricated and measured. A 3-dB gain bandwidth of 9.52%, from 100 GHz to 110 GHz, is achieved. The measured maximum gain at 105 GHz is 22.76 dBi, which gets an 8-dB enhancement with respect to the primary feed, without expanding the radiation aperture size. This method considerably reduces the complexity of TA and achieves a much more compact structure.

Detection Performance Of LT-GaAs-on-Silicon Bowtie Photoconductive Antenna Prototype

Jessica Afalla1; Alexander De Los Reyes2; Maria Angela Faustino2; Victor DC Vistro2; Hannah Bardolaza2; Gerald Angelo Catindig2; Karl Cedric Gonzales2; Elizabeth Ann Prieto2; Joselito Muldera3; Valynn Mag-usara4; Neil Irvin Cabello2; Vernalyn Copa2; John Paul Ferrolino2; Garik Torosyan5; Takashi Furuya4; Hideaki Kitahara4; Armando Somintac2; Arnel Salvador2; Masahiko Tani4; Elmer Estacio2
1University of Fukui, Japan; 2University of the Philippines Diliman, Philippines; 3de la Salle University, Philippines; 4University of Fukui, Japan; 5Photonic Center Kaiserslautern, Germany

We report on the detection characteristics of two bowtie photoconductive antennas which were fabricated on low temperature grown GaAs grown on Silicon substrates. The bowtie structure has a 10-µm antenna gap. The two samples have unique growth recipes, and were epitaxial grown on differently oriented substrates. The sample grown on a Si (100) substrate with a 4° tilt towards the (110) direction, has a longer carrier lifetime (24 ps) and higher detection intensity as a photoconductive antenna. The sample grown on a Si (100) substrate has a carrier lifetime of 13 ps. Its detection intensity was found to be lower, but its bandwidth slightly wider.

Combined UTC-PD Integrated On-chip THz Near Field Microscopy With Coupled Planar Goubau Lines

Tahsin Akalin1; Abdallah Chahadih2; Abbas Ghaddar2; Ibrahim Türer3
1Lille University, France; 2Lebanese University, Faculty of science, Lebanon; 3Airbus Defence and Space, Germany

In most of the cases for terahertz near field microscopy, a free space propagating electromagnetic wave interacts with a small tip placed above the sample. In our original approach, we use a guided way to bring the terahertz wave and to improve the interaction efficiency with the sample. The idea is to take benefit of the confinement around a Planar Goubau Line (PGL). We have fabricated a planar system with an integrated Uni-Travelling-Carrier Photodiode (UTC-PD) as a broadband source. The system can be used to map continuously at discrete frequencies the sample in a wide frequency range.

Characterization Of Smooth Dielectric Samples With Highly Focused Gaussian Beams In A Scatterometer

Michal Mrnka1; Per Heighwood Nielsen2; Tonny Rubæk2; Cecilia Cappellin2; Roger Appleby3; Elena Saenz1
1ESA-ESTEC, Netherlands; 2TICRA, TICRA, Denmark; 3Roger Appleby MMW Consulting Ltd., United Kingdom

This paper describes a numerical validation of the transmission coefficient of a smooth dielectric sample recently measured at ESA-ESTEC during the integration testing of a scatterometer operating in 50-750 GHz frequency range. The aim of the paper is to compare the experimental results of a calibrated measurement with a numerical model in GRASP and describe a numerical method for extracting material parameters.

Terahertz Near-Field Imaging Using Batch Fabricated Cantilevers With 70 Micrometers Long Tips

Benjamin Walter1; Estelle Mairiaux1; Dominique Vignaud2; Sophie Eliet2; Jean-Francois Lampin2; Marc Faucher2
1Vmicro SAS, France; 2Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, France

Batch fabricated atomic force microscopy cantilevers with tip longer than 70µm are reported. They are designed to increase terahertz focusing in scattering optical near field imaging. Terahertz SNOM imaging of sub-100nm features on a graphene sample is presented.

Terahertz Field Enhancement By Bull's Eye Antenna For Force-detected Electron Paramagnetic Resonance Measurements

Ren Fujioka1; Hideyuki Takahashi2; Kengo Sugahara3; Eiji Ohmichi1; Hitoshi Ohta2
1Graduate School of Science, Kobe University, Japan; 2Molecular Photoscience Research Center, Kobe University, Japan; 3School of Science and Engineering, Kindai University, Japan

We designed bull's eye antenna structure working at THz frequencies for use in force-detected EPR measurement, and numerically confirmed that the oscillating magnetic field B1 was focused into the subwavelemgth scale at the aperture with an enhancement by one order.

Passive Millimeter-wave Microscopy Of Aqueous Protein Solutions at Low Temperatures

Tatsuo Nozokido1; Yuya Takakura1; Akio Kishigami2
1University of Toyama, Japan; 2Gifu Women's University, Japan

Thermal radiation emitted from aqueous solutions of bovine serum albumin (BSA), which is a serum albumin protein derived from cows, was measured and analyzed by passive millimeter-wave microscopy at temperatures below the freezing point of water. The thermal radiation emitted from BSA aqueous solutions with different concentrations was measured at 50 GHz and temperatures ranging from 130 K to 260 K. Two different conformational states of the BSA were observed. The emissivities of the BSA solutions were successfully determined from the measured results.

Compressed Sensing Image Reconstruction For Millimeter-wave Near-field Scanning Microscopy Using A Metal Slit Probe

Tatsuo Nozokido1; Hiroki Okano1; Hiroyuki Kudo2
1University of Toyama, Japan; 2University of Tsukuba, Japan

We report on the use of a compressed sensing technique for two-dimensional image reconstruction in millimeter-wave near-field scanning microscopy that enables the measurement time required to acquire the projection data sets to be reduced. Experiments performed at 60 GHz to image the electrical response anisotropy of the sample using compressed sensing image reconstruction show that just 1/8th of the full scan data needs to be measured to allow perfect image reconstruction.

Propagation characteristics of high-throughput terajet beam and its super Resolution THz imaging

Qingshan Qu1; Bin Cui1; Zhenwei Zhang2; Yuping Yang1; Zhichao Yang1
1Minzu University of China, China; 2Capital Normal University, China

Broad-bandwidth spectral analysis is one of important advantages of terahertz (THz) imaging technology, while low spatial resolution restricts its further applications. In contrast to the contradiction between the high-resolution and the low-throughput as well as narrow-bandwidth in the existing THz near-field imaging technologies, a high-resolution, high- throughput and broad-bandwidth terahertz imaging method is proposed in this work based on the terajet effect produced by a dielectric semi-sphere with appropriate refractive index. The terajet beam can break through the restriction of the diffraction limit on the spatial resolution of the microscopic system without losing the energy and spectral width.

TeraFET Multi-pixel THz Array For A Confocal Imaging System

Dovilė Čibiraitė1; Min Wan2; Alvydas Lisauskas3; Adam Rämer4; Sergey Chevtchenko4; Wolfgang Heinrich4; Hartmut G. Roskos1; John T. Sheridan2; Viktor Krozer1; Viktor Krozer4
1Goethe University Frankfurt, Germany; 2University College Dublin, Ireland; 3Vilnius University, Lithuania; 4Ferdinand-Braun-Institut, Germany

We present a THz detector based on AlGaN/GaN HEMT technology implemented for a multi-pixel array and tested in a confocal THz imaging system. The multi-pixel array shows good homogeneity where the ratio between the most and the least sensitive pixels is less than two times. The detector has been tested in a confocal system at 300 GHz and the pictures show a good resolution.

Fabrication And Characterization Of Frequency Selective Terahertz Focal Plane Array And Camera

Hassane Oulachgar; Jacques-Edmond Paultre; Marc Terroux; Francis Provençal; Bruno Fisette; Hélène Spisser; François Berthiaume; Alex Paquet; Michel Doucet; Michel Jacob; Linda Marchese; Francis Généreux; Paul Grenier; Christine Alain; Alain Bergeron
National Optics Institute, Canada

A high performance frequency selective focal plane array (FPA) detector has been developed at INO. The detector array was fabricated using a CMOS compatible microfabrication process. The FPA consists of a 384x288 pixel array, with optimal detection frequency at 515 GHz. The radiometric performance of the detector, at this frequency, was improved by more than five-fold compared to previously reported frequency selective terahertz detector [2].

Modeling And Simulation Of Dielectric Whispering Gallery Mode Sensor Using Finite Element Method At THz Frequency

Himanshu Gohil1; Anushree Singh1; Cijy Mathai2; Niraj Joshi3; Shriganesh Prabhu1
1Tata Institute of Fundamental Research, India; 2Indian Institute of Technology - Bombay, India; 3SCEM, Mangalore, India

The design and optimization of Whispering Gallery Mode Resonator (WGMR) sensors in the THz regime can be modelled using Finite Element Analysis. In this paper, we have modelled and simulated a rectangular cross section ring WGMR and its response for the biomolecule analyte 'BSA' (Bovine Serum Albumin) at the THz frequencies. We design our resonator model for working frequency of around 0.161 THz using dielectric core with Refractive Index of 1.473, corresponding to HDPE and use the experimentally obtained refractive index of analyte. The simulation results after placing the analyte near the resonator evokes a response in the form of a characteristic peak frequency shift of 80 MHz and line broadening (~3x FWHM). These theoretical results can be used to study and obtain parameters to fabricate optimized devices which can yield results for sensing unlabeled analytes with low concentration and high specificity.

A GO/FO Tool For Analyzing Quasi-Optical Systems In Reception

Huasheng Zhang; Shahab Oddin Dabironezare; Giorgio Carluccio; Andrea Neto; Nuria Llombart
Delft University of Technology, Netherlands

In this work, a free accessible MATLAB interface is presented to analyze antenna-coupled Quasi-Optical (QO) systems in reception. This goal is achieved by using Fourier Optics (FO) and Geometrical Optics (GO) based methods. Specifically, the FO method represents the field focalized by a QO component on its focal plane as a plane wave spectrum when the component is illuminated by an incident field. This spectrum is related to the field scattered by the QO component which is calculated here using a GO method. By using this spectrum, the tool estimates the power received by an antenna placed at the focal plane of the QO component. Moreover, the performance in reception is evaluated.

Terahertz Imaging Based On Coherent Detection Of The Fourier-Space Spectrum

Hui Yuan1; Daniel Voß1; Min Wan2; Alvydas Lisauskas3; Hartmut G. Roskos1; John T. Sheridan2
1Physikalisches Institut/Johann Wolfgang Goethe-Universität, Germany; 2School of Electrical & Electronic Engineering / University College Dublin, Ireland; 3Institute of Applied Electrodynamics & Telecommunications / Vilnius Univ., Germany

A novel continuous-wave THz imaging system based on the coherent recording of the Fourier space spectrum (FSS) with heterodyne detection is described. The system consists of two 300-GHz electrical multiplier-chain sources with a slight frequency offset, and a single narrow-band TeraFET detector working in raster-scanning mode. The complex-valued FSS is recorded in either the focal-plane or in the free space of the optical system in focusing and non-focusing mode, respectively. Two- and three-dimensional (2D and 3D) images are reconstructed numerically with an inverse Fourier transform algorithm. With a 80×80-mm2 detection area and 1-mm2 sampling steps, 1-mm resolution and 76.2×76.2-mm2 image area are achieved.

Tunable Filter Design For IR Hyperspectral Imaging

Justine Champagne; Samuel Dupont; Joseph Gazalet; Jean-Claude Kastelik
IEMN, France

The use of wide-angle Acousto-Optic Tunable Filter (AOTF) for hyperspectral imaging is considered: the diffraction efficiency is calculated around a usual diffraction plane for two degrees of freedom (azimuthal and transverse angle). The efficiency evolution is also examined over a wide wavelength band. The diffraction efficiency is determined as a function of the incident angles and the results are commented.

3D Inspection Of Fiber-Reinforced Thermoplastics At THz Frequencies

Matthias Kahl; Jan Boecking; Bernd Engel; Peter Haring Bolívar
University of Siegen, Germany

Utilizing composite materials instead of metals allows to reduce weight while maintaining mechanical strength. Fiber-Reinforced Thermoplastics (FRT) have very competitive mechanical properties and additionally offer the capability for mass production, which makes the material particularly attractive in the automotive and aircraft sectors. Typical defects in FRT are dominated by fiber shifts and cracks. We show that 3D THz imaging using a FMCW approach can resolve such defects and is therefore a suitable tool for nondestructive testing applications, specifically for the quality control in FRT mass production.

A Convolutional Neural Network For The Non-destructive Testing Of 3Dprinted Samples

Mostafa Elsaadouny; Jan Barowski; Ilona Rolfes
Ruhr University Bochum, Germany

The three dimensional printing is a very important technology that participates in many applications. In this paper we present an approach for the Non-Destructive Testing (NDT) of the three dimensional printed objects. This methodology solves the image classification problem by using the Neural Networks (NN). The network has been trained by large data matrix which contains information about the mean, the variance and the pixel intensity of the input. The proposed solution has been used for testing different data sets for monitoring the performance under different scenarios, and the obtained results show high degree of accuracy regarding defects detection.

High Responsivity And Low NEP Of Room-Temperature Terahertz Antenna-Coupled Microbolometers With Meander Titanium Thermistor

Norihisa Hiromoto1; Amit Banerjee2; Durgadevi Elamaran1; Makoto Aoki3; Catur Apriono4; Hiroaki Satoh1; Erik Bruendermann5; Eko Rahardjo4; Hiroshi Inokawa1
1Shizuoka University, Japan; 2National University of Singapore, Singapore; 3National Institute of Information and Communications Technology (NICT), Japan; 4Universitas Indonesia, Indonesia; 5Karlsruhe Institute of Technology (KIT), Germany

In order to realize room-temperature terahertz (THz) detectors with high-detectivity, we have studied room- temperature THz antenna-coupled bolometers with titanium (Ti) meander-line thermistor fabricated on a high-resistivity silicon (Si) substrate by MEMS structures. In this paper, we report the spectrum of responsivity which spreads in the range of 0.1 THz width around 1 THz and it has high-responsivity bands with the orders of 1000 V/W. Thanks to the high responsivity and low noise of the metal thermistor, we have achieved good noise-equivalent power (NEP) of the order of 10^-11 W/Hz^1/2 and response speed of 5 kHz for the room-temperature antenna-coupled bolometers with Ti meander thermistor 0.1 µm-wide and 90 µm-long.

Incoherent Power Combining Of THz Source Arrays

Robin Zatta1; Ritesh Jain2; Daniel Headland3; Ullrich Pfeiffer1
1Institute for high frequency & communication technology, Germany; 2Bergische Universität Wuppertal, Germany; 3Graduate School of Engeneering Science of Osaka University, Japan

In this paper, we investigate the multi-chip scaling of a previously developed incoherent 4x4-pixel 0.53-THz 1- mW source array, implemented in a 0.13-um SiGe BiCMOS technology. A standalone module under-samples the illumination space due to a large pixel pitch given by the implemented triple-push oscillator topology coupled with narrow pixel beams. Therefore, we present the concept of super-array configurations by arranging multiple source arrays, achieving an increased fill factor, increased radiated power, and wider illumination aperture. Moreover, such super-array configurations can help to reduce the influence of spurious reflections at THz frequencies by providing a diffused radiation. For a 2x1 super-array, the 10-dB fill factor increased from 10.9 to 61.8% while maintaining the illumination aperture; and the net radiated power doubled to 2 mW (3 dBm). For a 2x2 super-array, the illumination aperture quadrupled; the radiated power and the 10-dB fill factor at 0.53 THz were 4 mW (6 dBm).

Kernel Size Characterization For Deep Learning Terahertz Tomography

Yi-Chun Hung1; Shang-Hua Yang2
1National Tsing-Hua University, Taiwan; 2Department of Electrical Engineering, National Tsing Hua University, Taiwan

We present supervised terahertz deep learning models for high-precision terahertz tomography. To investigate the performance of terahertz deep learning models, comprehensive characterization of kernel size in first convolution layers is further studied. By utilizing the length of beam diameter, the optimized kernel size can be designed to deliver the much spatially accurate images, which achieves 2.5% on mean square error (MSE) , 46.8% improvement on MSE than other kernel size.

340 GHz And 250 GHz Schottky Solid-state Heterodyne Receiver Arrays For Passive Imaging Systems

Yue He1; Li Wei Hou2; Yao ling Tian1; Kun Huang1; Jun Jiang1
1Microsystem and Terahertz Research Center, China; 2The 50th research institute of china electronics technology group corporation, China

Two four-pixel receiver arrays for operation in 340 and 250 GHz passive imaging system are presented. The millimeter-wave front-end components and THz mixer are achieved by the planar GaAs Schottky-barrier varactor to obtain good performance in room temperature while lowering the cost and difficulty compared to integrated circuit. The discrete 340GHz and 250GHz mixers have the lowest DSB noise temperature of 1020K and 900K respectively within the operation band . A broadband IF bandwidth, 20GHz, is adopted in passive imaging systems for increasing the received human body radiation power. Good detection performance and space resolution is still obtained for object distances 3-8m. Compared to the current sensors operated in cryogenic imaging system, the receiver array is a cheap and feasible method for personal security screening

Broadband Bendable Terahertz Camera For Built-in Infrastructure Sensor

Daichi Suzuki1; Koji Ishibashi1; Yukio Kawano2
1RIKEN Center for Emergent Matter Science, Japan; 2Tokyo Institute of Technology, Japan

We present a broadband bendable THz camera, composed of a free-standing carbon nanotube film array, which is intended for an built-in infrastructure sensor. As advantages over conventional solid-state THz sensors, our bendable THz camera can be fabricated through simple and low-cost processes and can simplify optical/electrical measurement systems, which enables us to mount the sensor on objects regardless of their shapes, sizes, and locations. We demonstrate the use of our novel THz camera for real-time nondestructive imaging of industrial products, indicating possibilities of one of the powerful components such as built-in/wearable THz sensors for future imaging and remote sensing.

A Full-wave Analysis Of Lenses For THz Detectors Purposes

Pawel Kopyt1; Bartlomiej Salski1; Jerzy Cuper1; Przemyslaw Zagrajek2
1Warsaw University of Technology, Poland; 2Military University of Technology, Poland

In this work an analysis of power density inside various types of lenses is presented. Properties of structures commonly used in THz detectors have been verified using a full-wave EM simulations. Two alternative implementations of EM solvers have been considered. Possibility of replacing spherical-based structures with more sophisticated elliptical lenses were considered as well, showing similar properties

THz Super-Resolution Imaging With Parallel-Pixel Data Acquisition For Rapid Inspection Applications

Rungroj Jintamethasawat; Chayut Thanapirom; Patharakorn Rattanawan; Napat Cota; Natcha Cota; Chia Jia Yi; Kittipong Kasamsook
National Electronics and Computer Technology Center, Thailand

A multi-frame, super-resolution imaging algorithm for a THz array detector with parallel-pixel data acquisition is proposed to overcome both detector resolution limit and prolonged acquisition time. A correction scheme was also implemented to counteract a fixed-pattern noise caused by non-uniform pixel responsivity observed in our experimental results. The proposed technique aims to serve the demands for THz non-destructive testing (NDT) and quality control (QC) applications, which requires a rapid high-resolution THz imaging system.

A Terahertz Superconducting Single-Pixel Imaging System Using DMD

Yilong Zhang; Yuan Ren; Wei Miao; Hao Gao; Shengcai Shi
Purple Mountain Observatory, Chinese Academy of Sciences, China

We propose a terahertz superconducting single-pixel imaging system with a single hot electron bolometer (HEB) detector combined with a digital-mirror-device (DMD). With the DMD as a programmed coding reflector, the proposed imaging system could acquire coded measurement results of an imaged scene rapidly even with a single detector. Base on compressive sensing (CS) techniques, the imaged scene was reconstructed by fewer coded measurements compared to the image size. We demonstrated that the proposed single-pixel imaging system framework could significantly improve the imaging efficiency and resolution.

The Design Of W Band Dual Polarization Parabolic High Gain Antenna

Zhengxin Fang; Sen Feng

In this paper, a dual-polarization parabolic high-gain antenna in the W-band is designed. Dual polarized horn is used as feeds in the antenna in the antenna systems. A microstrip reflection array is attached to the parabolic column as a reflective surface. The antenna has dual polarization. In the azimuth direction, phase compensation is performed by the microstrip reflection array applied to the inner surface of the parabolic column, and lobe focusing is achieved together with the dual-polarized horn feed, in the elevation direction, lobe focusing is achieved by means of a parabolic surface on the elevation surface and a dual-polarized horn feed, the W-band far-field pattern is thus obtained. The antenna is 0.6m long and 0.6m wide. After tested, the sidelobe level is â?¤-25dB, the cross polarization is <-30dB, and the gain is >52.5dB in the bandwidth of 93.5GHz-95.5GHz. The antenna has compact structure, small volume, light weight, it is simple feeding, low cost .

Comparative Study Of Millimeter Wave III/V Semiconductor And Integrated Silicon Based FMCW Radars

Jean-Paul Guillet1; Frédéric Fauquet2; Jing Shun Goh2; Adrien Chopard2; Jean-Baptiste Perraud2; Marie Roux3; Patrick Mounaix2
1Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France; 2IMS Laboraotry, France; 3Atelier des renaissances, France

In this publication, we present comparative study of the last developments of frequency modulated continuous wave (FMCW) systems in the terahertz frequency range including GaAs based systems and SiGe integrated systems.

Study Of A THz Hollow-core Fiber For Sample Reflectance Analysis

Mingming Pan1; Cristiano M. B. Cordeiro2; Frédéric Fauquet1; Patrick Mounaix1; Gildo S Rodrigues2; Marcos A. R. Franco3; Jean-Paul Guillet4
1IMS Laboraotry, France; 2Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Brazil; 3Instituto Tecnológico de Aeronáutica-ITA, Brazil; 4Laboratoire IMS / Université de Bordeaux / CNRS UMR 5218, France

We investigated a 3D printed hollow-core THz waveguide with a suitable frequency band to be, in the future, associated with a guided reflectometry system.

Cooled Silicon-On-Insulator Diode Thermometer: Toward THz Passive Imaging

Jérémy Blond; Jérôme Meilhan; Abdelkader Aliane; Laurent Dussopt
CEA LETI, France

Terahertz passive imaging requires high sensitivity detectors, with Minimum Detectable Power (MDP) under the picowatt range. An antenna-coupled cooled microbolometer, incorporating a lateral PiN-like diode as thermometer, could represent a solution. In a first step, such diode performances have to be investigated, especially the temperature coefficient of current (TCC) and the low frequency noise. Prototypes were fabricated on Silicon-On-Insulator (SOI) 4" wafers with 50-nm active silicon layer. I-V and noise measurements down to 81K were useful to derive the electrical MDP of the future bolometer, already reaching 6.6 pW at 10 frames per second.

Continuous-wave Terahertz Computed Tomography Based On Bessel Beam

Lu Rong; Bin Li; Dayong Wang; Yunxin Wang; Jie Zhao; Xiaoyu Shi
Beijing University of Technology, China

We report a continuous-wave terahertz computed tomography using Bessel beam generated by the axicon. Two-dimensional cross-sectional images of the internal structure of plastic pipes at different distances are reconstructed by using the filtered back projection algorithm. Compared with conventional Gaussian beam, Bessel beam can extend the depth of field and improve the fidelity of the reconstruction.

Diffraction Of Terahertz Gaussian And Bessel Beams On 2D Gratings With Wavelength-Scale Openings

Oleg Kameshkov; Boris Knyazev; Igor Kotelnikov; Boris Goldenderg
Budker Institute of Nuclear Physics, Russian Federation

The diffraction of Gaussian and arbitrary-order Bessel wavefronts on the 2D periodic amplitude and phase gratings, including those with holes whose diameters are close to the wavelength, was investigated. When the amplitude grating is illuminated by a Bessel beam, the self-images of the grating in the main and fractional Talbot planes turn into lattices of rings whose radii depend in a complex way on the grating parameters and on the illuminating beam characteristics. The results of the experiments carried out using the wavelength-tunable radiation of the Novosibirsk free electron laser (NovoFEL) are in good agreement with the numerical calculations and the analytical model developed.

High Resolution Passive THz Imaging Array With Polarization Reusage In 22nm CMOS

Sven van Berkel; Satoshi Malotaux; Bart van den Bogert; Marco Spirito; Daniele Cavallo; Andrea Neto; Nuria Llombart
Delft University of Technology, Netherlands

A 12-pixel THz Focal Plane Array (FPA), integrated in Global Foundries 22nm CMOS technology, enabling high resolution passive THz imaging, is presented. The array efficiently couples blackbody radiation from 200 GHz to 600 GHz to Schottky Barrier Diodes (SBDs) in a differential topology. An antenna-detector co-design results in an average Noise Equivalent Power (NEP) of 0.9 pW/√Hz. An extremely small array periodicity is achieved by using two orthogonal polarizations. Such configuration enables passive imaging with a near-diffraction limited resolution while simultaneously maintaining a high optical efficiency of 42%. The array is currently in tape-out and measurements will be presented at the conference.

Full-field THz Polarimetric Imaging With THz Quantum Cascade Laser And THz Imager

Takahiko Mizuno1; Takuya Moriki2; Masatomo Yamagiwa2; Takeo Minamikawa1; Takeshi Yasui1
1Institute of Post-LED Photonics, Tokushima University, Japan; 2Faculty of Mechanical Engineering, Tokushima University, Japan

We demonstrate full-field THz polarimetric imaging with THz quantum cascade laser and THz imager. In contrast to point-scanning THz polarization imaging based on THz-TDS, the demonstrated method does not need mechanical stages for time-delay scanning and sample-position scanning. Due to no mechanical scanning, the fill-field polarimetric images are acquired with moderate frame rate.

Quantum Probability Theory Applied To Improve Terahertz Imaging Quality

Xuling Lin1; Zhi Zhang1; Jianbing Zhang2; Zhimin Dai2
1Beijing Institute of Space Mechanics and Electricity, China; 2Shanghai Institute of Applied Physics, Chinese Academy of Sciences, China

THz imaging plays an important role in astronomy, atmospheric remote sensing and biological identification. Improvement of imaging quality is of great significance to the application of terahertz imaging system. In this paper, on the basis of quantum probability statistics, an image enhancement method for improving terahertz imaging quality is proposed. Experimental results show that this method takes account of both global and local image information, and improves the quality of terahertz image effectively.

Terahertz Digital Holography Using Field-Effect Transistor Detectors

Yuchen Zhao1; Dmytro But2; Marc Georges1; Wojciech Knap3
1Centre Spatial de Liège, Université de Liège, Belgium; 2Center for Terahertz Research and Applications (CENTERA), Institute for High Pressure Physics,Polish, Poland; 3Laboratory Charles Coulomb, Montpellier University, France

We report on the experimental realization of digital holography at 140 GHz using terahertz detectors based on field-effect transistors. We demonstrate that hologram signal can be efficiently recorded by the FET detector at room temperature. The digital reconstructions of amplitude and phase objects are presented. Owing to the possibility for FET array integration and massive production, potential towards fast scan nondestructive testing application is discussed.

Genetic Algorithm Based Optimization For Terahertz Time-Domain Adaptive Sampling
Kaidi Li1; Xuequan Chen1; Rui Zhang2; Emma Pickwell-MacPherson3; Shuaiqi Shen1; Kai Liu1
1The Chinese University of Hong Kong, China; 2Shenzhen Institutes of Advanced Technology, Chines Academy of Science, China; 3The Chinese University of Hong Kong, Hong Kong and Department of Physics, The University of Warwick, the United Kingdom

We propose an approach based on a genetic algorithm (GA) to improve the sampling efficiency in terahertz time-domain spectroscopy (THz-TDS). The experimental results show that our approach can greatly reduce the sampling time whilst maintain a very high accuracy compared to high-resolution step scanning. Moreover, this approach can be easily implemented in most TDS systems equipped with a delay stage without any hardware cost. The accuracy, flexibility and efficiency indicate great potential for this approach to improve the scanning speed in a wide range of applications.

Hybrid Technique For Gas Sensing Based On Differential Cavity Ring Down Spectroscopy Sensitized With Thermal Lens Effect
Atsushi Yarai
Osaka Sangyo University, Japan

A new gas sensing technique based on a cavity ring down (CRD) spectroscopy is proposed. This technique features the hybrid operation for enhancing the sensitivity by amplifying the optical absorption efficiency with a thermal lens effect. At first, system configuration composed of optical fiber is presented. Then, the observed comb-like differential CRD signal which exhibits its capability definitely is shown. It is confirmed that the detectability is approximately 20 μmol/liter as the limit of detection value with P(13) absorption line of acetylene gas. It is a few-fold higher value compared with our conventional technique.

Metasurface-Based Anti-Alias Filters For Improved THz-TDS Measurements

Nazar Nikolaev1; Sergei Kuznetsov2; Alina Rybak3; Shang-Hua Yang4
1Institute of Automation and Electrometry SB RAS, Russian Federation; 2Rzhanov Institute of Semiconductor Physics SB RAS, Russian Federation; 3Novosibirsk State University, Russian Federation; 4Department of Electrical Engineering, National Tsing Hua University, Taiwan

We propose an approach to improve THz-TDS low-frequency measurements accuracy. It is based on applying anti-alias filters to narrow the frequency band of the THz signal that allows increasing the sampling interval in accordance with the Nyquist--Shannon theorem. The concept was verified by studying the transmittance spectra of the reference samples -- band-pass THz filters centered at 156 and 376 GHz. We show a reduction of the spectrometer scanning time by up to 12 times while maintaining the measurement accuracy. The prospects for using this approach to increase the dynamic range and the signal-to-noise ratio of the spectrometer in the subterahertz range are discussed.

Optical Heterodyne Detection In The Terahertz Region For Accurate Frequency Measurement

Shin'ichiro Hayashi; Shingo Saito; Norihiko Sekine
National Institute of Information and Communications Technology, Japan

We propose an optical heterodyne detection in the terahertz region using parametric up-conversion in a nonlinear LiNbO3 crystal for accurate frequency measurement. Nonlinear wavelength up-conversion techniques based on frequency stabilized infrared pumping beam allow the spectra in the terahertz region to be determine their frequency and intensity. These are very promising for extending applied research into the terahertz region, and we expect that these will open up new research fields such as wireless information communications in the terahertz region.

Combination Of Adaptive Sampling Terahertz Dual-Comb Spectroscopy With A Free-Running Single-Cavity Dual-Comb Fiber Laser

Jie Chen; Kuzuki Nitta; Xin Zhao; Takahiko Mizuno; Takeo Minamikawa; Zheng Zheng; Takeshi Yasui
Beihang University, China

Mode-resolved adaptive sampling terahertz dual comb spectroscopy is demonstrated using a free-running wavelength-multiplexed dual-comb fiber laser, indicating the capability of such single-cavity dual-comb sources for high-precision THz spectroscopy.

Frequency Measurement For Terahertz Waves Based On The High Magnetic Field Technology

Xin Qi; Houxiu Xiao; Xiaotao Han; Donghui Xia; Pengbo Wang; Xianfei Chen
Huazhong University of Science and Technology, China

A novel method based on the Zeeman Effect has been proposed for the frequency measurement in the THz range. We convert the frequency measurement into magnetic field measurement. In theory, the measurement range can cover the entire THz range as the magnetic field meets the requirement. Using this method, we demonstrate an accuracy of our measurement system as high as 0.01% for the measurement of a 120GHz source, no matter it work at a continuous regime or a pulse regime.

Uncertainty Quantization Of Fano Resonance Frequency Shift Measurement

Tuan Anh Pham Tran; Elana Pereira de Santana; Peter Haring Bolívar
University of Siegen - High Frequency and Quantum Electronics, Germany

We describe and characterize a Fano-resonance frequency shift measurement setup at 300GHz for ex-situ biomolecule detection applications. By quantifying experimental contributions from each uncertainty source, trade-offs can be adapted to achieve the desired system stability requirements. We obtain a 10 MHz standard deviation in determining resonance position with repeated sample exchange and repositioning, and determine the future to attain a 2 MHz frequency shift precision at 300GHz.

Dual-band Electromagnetically Induced Transparency Effect In Asymmetrically Coupled Terahertz Metamaterials

Dipa Ghindani1; Rakesh Sarkar2; Monika Devi Koijam2; Ravikumar Jain3; Arnab Pattanayak3; Shriganesh Prabhu3; Gagan Kumar2
1Tata Institute of Fundamental Research, India; 2Department of Physics, Indian Institute of Technology Guwahati, India; 3Tata Institute of Fundamental Research, Foton Lab, India

In this article, we propose a metamaterial geometry capable of exhibiting dual-band electromagnetic induced transparency (EIT) effect in terahertz frequency regime. The meta-molecule unit consists of two C resonators of different dimensions, placed alternately on both sides of a cut-wire (CW). Our study can play an important role in the development of multi-band slow light devices and also for sensing applications.

THz Wave Generation In Nonlinear Crystal ?eta-BBO

Jingguo Huang1; Zhiming Huang1; Yury Andreev2; Grigory Lanskii2; Dmitrii Lubenko3; Nazar Nikolaev4; Valery Losev3
1Shanghai Institute of Technical Physics CAS, China; 2Institute of Monitoring Climatic and Ecological Systems SB RAS, Russian Federation; 3Institute of High Current Electronics SB RAS, Russian Federation; 4Institute of Automation and Electrometry SB RAS, Russian Federation

Nonlinear crystals of beta-barium borate, beta-BBO (further BBO) are widely used to generate THz radiation in a laser filament in two-color optical systems, in which BBO is used to for the second harmonic generation of the pump radiation. It should be outlined that BBO crystal can be used for frequency conversion of visible - IR laser emissions into the THz range in accordance with the recent study. Possessing high damage threshold, despite of low nonlinear coefficients, BBO crystal can be considered as an effective nonlinear crystal for THz generation by parametric nonlinear processes. In this experiment, the THz pulses are realized from BBO crystal pumped by 10-mJ Ti: Sapphire laser complex operating at 950 nm at room temperature. Generation is achieved in spectral range 0.25-0.8 THz.

15NH3 Terahertz Gas Laser Pumped By A Mid-infrared Quantum-Cascade Laser

Martin Wienold; Alsu Zubairova; Heinz-Wilhelm Hübers
German Aerospace Center (DLR), Germany

We present an optically pumped terahertz gas laser, which is based on a distributed-feedback mid-infrared quantum-cascade laser as a pump source, a standing wave resonator, and 15NH3 as a gain medium.

High Performance Terahertz Absorption Of Nanostructured NiCr Film For A Pyroelectric Detector

Ziji Liu; Zhiqing Liang; Xing Zheng; Yadong Jiang
University of Electronic Science and Technology of China, China

Nanostructured metallic films is an effective THz absorption layer for pyroelectric detectors.The THz responsivity for detector tested by lock in amplifier reaches 8.38Ã-104V/W and the lowest noise equivalent power value(NEP) reaches 1.27Ã-10-10W/Hz1/2 at 20Hz operating frequency use 2.52THz radiation, which is suitable for THz imaging application. Meanwhile it provides a feasible approach for fabricating high responsivity THz detector

A Novel Terahertz Microfluidic Chip

Bo Su; Jiahui Wang; Yiwei Wen; Jingsuo He; Shengbo Zhang; Cunlin Zhang
Capital Normal University, People's Republic of China, China

we fabricate a new terahertz microfluidic chip, which can detect liquid samples using THz-TDS system or asynchronous optical sampling system. The chip has a sandwich structure, and consists of substrate, cover and microchannel layer. The substrate and cover are made of two materials, PMMA and cycloolefin copolymers (COC). The microchannel layer is fabricated by PDMS. Through van der Waals force, the substrate, cover and microchannel layer are sealed together. We use the chip to study the transmission of terahertz to deionized water and the influence of different kinds and concentration of electrolyte solution on hydrogen bond in aqueous solution, and the results prove the feasibility of this method.

Quasi-Optical Design Of ECRH Mirrors For ITER First Plasma Operations

Francesco Fanale1; Alessandro Bruschi1; Olivier Darcourt2; Daniela Farina1; Lorenzo Figini1; Franco Gandini3; Mark Andrew Henderson3; Ryan Hunt3; Alessandro Moro1; Paola Platania1; Burkhard Plaum4
1Consiglio Nazionale delle Ricerche - Istituto di Fisica del Plasma, Italy; 2Arial Industries, France; 3ITER Organization, France; 4Universität Stuttgart - Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Germany

A set of components will be installed during ITER fist plasma operation to protect the vacuum vessel and other in-vessel auxiliary systems from the plasma and from the stray radiation injected at the Electron Cyclotron harmonics to generate breakdown and sustain burn-through. This paper focuses on the quasi-optical design of the system of three mirrors redirecting the microwave beams coming from the Electron Cyclotron Resonance Heating (ECRH) upper launcher to the plasma resonance after proper shaping. In particular, the system consists of two shaped mirrors and one grating mirror. The non-absorbed EC power is then intercepted and absorbed into a beam dump located in one equatorial port.

Terahertz Filter With Flat-top Transmission Response
Antonio Ferraro1; Alfonso A. Tanga2; Dimitrios C. Zografopoulos1; Gabriele C. Messina3; Michele Ortolani2; Romeo Beccherelli1
1Consiglio Nazionale delle Ricerche - Istituto per la Microelettornica e Microsistemi CNR-IMM, Italy; 2Department of Physics, Sapienza University of Rome, Italy; 3Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi (CNR-ISC), Italy

A new terahertz filter based on the coupling of guided-mode resonances and Fabry-Perot resonance is presented resulting in a flat top response. The spectral response lies in the sub-THz communication windows with central frequency of 300 GHz. The filter performance shows high transmittance, with less than 3dB losses, and high out-of-band rejection. The filter is fabricated via standard photolithography on thin films of the Zeonor polymer. This typology of THz components provides a cost-effective functional solution for narrowband filtering in emerging THz devices and systems for telecommunication.

Polarization And Sectioning Characteristic Of THz Confocal Microscopy

Min Wan1; Dovilė Čibiraitė2; Bing Li3; Hui Yuan2; Viktor Krozer2; Hartmut Roskos2; Da Yong Wang3; John Sheridan1
1School of Electrical & Electronic Engineering, University College Dublin, Ireland; 2Physikalisches Institut, Goethe University Frankfurt, Germany; 3College of Applied Sciences, Beijing University of Technology, China

A 300 GHz confocal microscope has been implemented and tested consistent lateral and axial spatial resolution under difference polarization have been demonstrated.

Generation And Measurement Of Traceable THz Frequencies

Gregory Gäumann; Jacques Morel
Federal Institute of Metrology METAS, Switzerland

The THz radiation is generated by optical heterodyning of two lasers in a phomixer and the frequency traceability is achieved either by measuring the laser frequencies with a traceable wavemeter or by directly referencing the two lasers to a self-referenced optical frequency comb (OFC) locked to an atomic clock. This method will allow achieving a relative THz frequency uncertainty below 8?10-9.

Tail-suppressed THz Photocurrent By A Bi-polar Photoconductive Antenna Fabricated On Semi-insulating GaAs

Anup Kumar Sahoo
1; Hsiao-Hua Wu2; Yu-Cheng Hong1; Yu-Chen Chang1; Osamu Wada3; Ci-Ling Pan1
1Department of Physics, National Tsing Hua University, Taiwan; 2Department of applied physics, Tunghai University, Taiwan; 3Office for Academic and Industrial Innovation (Oacis), Kobe University, Japan

We designed and fabricated bi-polar type photoconductive antenna (PCA) for efficient generation of broadband terahertz (THz) radiation. The falling time of overlayingly generated photocurrent from bi-polar PCA can be achieved 200 fs via superimposing two primariy opposite polarity photocurrent pulses having falling time of 100 ps with time delay of 200 fs. The simulation results disclosed a possibility to shift the central frequency from 0.1 to 1.3 THz and enhance the THz power by twice in the range 1.5 - 3.3 THz by using low cost substrate with long carrier life time such as semi-insulating gallium arsenide (SI-GaAs).


THz To Inspect Graphene And Thin Film Materials
Miguel Laso
1; Álvaro Cordón2; Luis Miranda2; Cristian Martínez2; Andrea Inés2; David Etayo2; Montserrat Fernández2; Pablo Rodríguez2; Elena Taboada2; Albert Redó-Sánchez2; Mónica Castrillo2; Israel Arnedo2
1Public University of Navarre (UPNA), Dept. Electrical, Electronic and Communications Eng., Spain; 2das-Nano, Spain

In this paper, we present a system that provides meso-scale characterization of thin film materials, covering the gap between nano-scale and macro-scale methods. Nano-scale methods are slow and cannot characterize large surfaces. Macroscale methods generate characterization that averages the magnitudes and, thus, cannot provide localized information. Our system works in reflection as opposed to state-of-the-art methods and provides mobility, carrier density, and conductance maps in the THz range. Moreover, it can be integrated with reactors and enables monitoring of the fabrication of materials in real-time, supporting, for instance, the production of graphene at industrial scale.

Excitonic Terahertz Emission From Silicon At Steady-State Interband Photoexcitation

Alexey Zakhar'in; Alexander Andrianov
Ioffe Institute, Russian Federation

Terahertz range photoluminescence from specially designed structures with tunnel coupled double quantum wells under interband optical excitation has been investigated. A series of narrow emission lines were observed and interpreted as intersubband radiative transitions between electron quantum confinement levels.


Wednesday 4 September 2019


09:00-10:30 - Plenary Sessions - Amphi Lavoisier

Chairperson: Jean Léotin

09:00 We-Pl-1

Terahertz Physics Of Graphene, Possibly The Most Nonlinear Material We Know

Dmitry TURCHINOVICH, Bielefeld University, Germany

09:45 We-Pl-2 Optically-Pumped Terahertz Sources And Applications

Jean-François LAMPIN, IEMN Lille, France

10:30-11:00 - Coffee Break

11:00-12:30 - Parallel sessions We-AM

11:00-12:30 -  We-AM-1- THz Water - Room 101

Chairperson: Xavier Ropagnol

11:00 We-AM-1-1
Hertz-to-terahertz Dielectric Response Of Nanoconfined Water Molecules
Mikhail Belyanchikov1; Maxim Savinov2; Petr Bednyakov2; Zakhar Bedran1; Victor Thomas3; Victor Torgashev4; Anatoly Prokhorov1; Alois Loidl5; Peter Lunkenheimer5; Elena Zhukova1; Ece Uykur6; Martin Dressel6; Boris Gorshunov1
1Moscow Institute of Physics and Technology, Russian Federation; 2Institute of Physics AS CR, Czech Republic; 3Institute of Geology and Mineralogy RAS, Russian Federation; 4Southern Federal University, Russian Federation; 5University of Augsburg, Germany; 6Universität Stuttgart, Germany

Broad-band dielectric spectroscopy is applied to study excitations of interacting electric dipoles spatially arranged in a network with an inter-dipole distance of 5-10 Å. The dipoles with magnitude of 1.85 Debye are represented by single H2O molecules located in voids (0.5 nm size) formed by ions of the crystal lattice of beryl and cordierite. Rich sets of single-particle and collective excitations are discovered and their origin analyzed.

11:30 We-AM-1-2
Collective Dynamics Of Nanoconfined Water In Phospholipid Multilamellar Vesicles Studied By Broadband Dielectric Relaxation Spectroscopy
Kihoon Eom; Jeongmin Jang; Seonmyeong Kim; Gun-Sik Park
Seoul National University, Republic of Korea

We present the first experimental characterization, using GHz to THz dielectric relaxation spectroscopy, of the collective rearrangement of the hydrogen bond network of water molecules nanoscopically confined in phospholipid multilamellar vesicles. We determined a distinct relaxation peak at ~40 GHz and the Kirkwood correlation factor of approximately 1.13, which are the indication of acceleration of the collective reorientation dynamics with nanoconfinement, and complete disruption of the hydrogen bond network compared with that of bulk water. Combined with X-ray observation, it has estimated that ~68% of the nanoconfined water contributes to the accelerated relaxation mode.

11:45 We-AM-1-3
Intermolecular Probe For The Structural Deformation Of Liquid Water Around Highly Charged Ions

Vasileios Balos; Martin Wolf; Mohsen Sajadi
Fritz Haber Institute of the Max Planck Society, Germany

We employ nonlinear THz spectroscopy to study the impact of highly charged ions on the hydrogen-bonding network of liquid water. We monitor the change of the THz induced optical birefringence of water in the presence of strongly charged anions and cations. We correlate the ionic effect to the strengthening / weakening of the coupling between the rotational and the translation motions in the liquid. The latter intermolecular probe, clearly shows opposite anionic versus cationic effect and enable us to provide a novel insight on the structure making / breaking behavior of ions.

12:00 We-AM-1-4
Quantum Critical Behavior Of Nanoconfined Water Molecules

Elena Zhukova1; Mickhail Belyanchikov1; Maxim Savinov2; Peter Bednyakov2; Jan Prokleska2; Stanislav Kamba2; Zakhar Bedran1; Victor Thomas3; Victor Torgashev4; Ece Uykur5; Martin Dressel5; Boris Gorshunov1
1Moscow Institute of Physics and Technology, Russian Federation; 2Institute of Physics AS CR, Czech Republic; 3Institute of Geology and Mineralogy, RAS, Russian Federation; 4Faculty of Physics, Southern Federal University, Russian Federation; 5Physikalisches Institut, Universität Stuttgart, Germany

We have studied terahertz and radio-frequency dielectric response of single water molecules periodically arranged in nano-cages formed by the crystal lattice of beryl. Below ~20 K, quantum effects start to dominate the properties of the H2O dipolar system as manifested by a crossover between the Curie-Weiss and the Barrett regimes in the temperature behavior of the dielectric permittivity ε'. Analyzing the temperature evolution of the inverse permittivity ( ε')^-1 down to T = 0.3 K, we discover signatures of quantum critical behavior of coupled water molecular dipoles: its quadratic variation with temperature at T=3-12 K and a shallow minimum in the ( ε')^-1(T) dependence below 3 K.

12:15 We-AM-1-5
Hydration Numbers From Ab Initio Water Reorientation Dynamics

Seonmyeong Kim1; Jeongmin Jang1; Kihoon Eom1; Devis Di Tommaso2; Gun-Sik Park1
1Seoul National University, Republic of Korea; 2Queen Mary University of London, United Kingdom

We present a novel approach to determine the hydration number of aqueous electrolytes by means of ab initio molecular dynamics. An hydration status analysis is devised to quantify the cooperative effect of ions on the reorientational dynamics of different water subpopulations in electrolyte solutions. The methodology is applied to predict the hydration numbers, h, as the number moles of water molecules per mole of dissolved salt that no longer participate in bulk-like reorientational dynamics. The obtained hydration number of MgCl2 (h = 15) is consistent with THz-DR experiment, measuring reorientational dynamics of water in solutions. By providing a link with the micro-scale dynamical behaviour of ions and water molecules, this approach represents a generally applicable, well-defined methodology to quantify hydration numbers of ions and molecules in aqueous solutions.

11:00 - 12:30 We-AM-2 - PC Devices 1 - Room 162

Chairperson: Nuria Llombart-Juan

11:00 We-AM-2-1
Highly Efficient Scalable Semiconductor Terahertz Sources
Gyula Polonyi1; Priyo Nugraha1; Nelson Mbithi1; Gergő Krizsán1; Balázs Monoszlai2; György Tóth1; Mátyás Mechler1; János Hebling1; József Fülöp1
1University of Pécs, Hungary; 2ELI-ALPS, ELI-Hu Nonprofit Ltd., Hungary

Highly efficient generation of intense THz pulses from infrared-pumped semiconductor sources is presented. Concepts of increasing the efficiency and peak electric fields for single- and multicycle THz waveforms are discussed.

11:30 We-AM-2-2
Generation Of A Guided Mode In A THz Semiconductor Waveguide using Excitation By A Tilted Optical Pulse Front
Gamar-ul Islam; Fanqi Meng; Hartmut G Roskos
Goethe University Frankfurt, Physikalisches Institut, Germany

We employ tilted-pulse-front techniques to control the propagation direction of the THz pulses emitted from photoexcited semiconductors. At a proper tilt angle of the optical pulse front, the generated THz pulse propagates along a waveguide on the semiconductor surface and eventually emits from the end facet of the semiconductor structure. This work aims at an investigation of semiconductor quantum structures with gain excited just in time when the THz pulse to be amplified arrives

11:45 We-AM-2-3
Advanced Photoconductive Terahertz Near-field Microprobes For 1550 Nm Wavelength Operation Based On InGaAs:Rh

Michael Nagel1; Alexander Michalski1; Simon Sawallich1; Robert B. Kohlhaas2; Björn Globisch2
1Protemics GmbH, Germany; 2Heinrich Hertz Institut, Germany

Photoconductive microprobes have been widely established in recent years for surface-near THz field measurements with sub-wavelength resolution and applications such as wafer scanning or metamaterial characterization. Since the standard material for these probes is still LT-GaAs, the optical pump wavelength is usually set below 890 nm for direct bandgap excitation. Adaption to modern fiber-based THz TDS systems --operating at 1550 nm -- required the use of optical frequency doubling components, so far. In this work, we investigate an alternative solution based on InGaAs:Rh for direct operation at 1550 nm wavelength.

12:00 We-AM-2-4
Photoconductive Arrays For High-Field Terahertz Generation
David Bacon; Mark Rosamond; Thomas Gill; Andrew Burnett; Lianhe Li; John Cunningham; Edmund Linfield; Giles Davies; Paul Dean; Joshua Freeman
University of Leeds, United Kingdom

We report on the development of a large-area photoconductive THz array structure with an LT-GaAs active region fabricated on quartz substrates using a BCB bonding process. These generate high THz-fields with a bandwidth greater than 5 THz.

12:15 We-AM-2-5
Rapid, Accurate And Precise Terahertz Polarization Modulation And Ellipsometry With Multi-pixel Interdigitated Photoconductive Emitters

Connor Mosley; Michael Staniforth; Arturo Hernandez-Serrano; Emma Pickwell-MacPherson; James Lloyd-Hughes
University of Warwick, United Kingdom

We demonstrate that multi-element interdigitated photoconductive emitters can rapidly and precisely modulate broadband terahertz radiation between linear (horizontal or vertical) and circular polarization states. The rapid electrical modulation between polarization states is beneficial for THz time-domain spectroscopic ellipsometry: it eliminates mechanical rotation and enhances the relevant figures of merit.

11:00 - 12:30 We-AM-3 - High Fields 3 - Amphi Lavoisier

Chairperson: Koichiro Tanaka

11:00 We-AM-3-1

Examining Nonlinear Terahertz Photonic And Phononic Excitation With Two-Dimensional Spectroscopy
Brittany E. Knighton; Megan Nielson; Courtney L. Johnson; Lauren Rawlings; Aldair Alejandro; R. Tanner Hardy; Clayton D. Moss;
Jeremy A. Johnson
Brigham Young University, United States

We use high-field, broadband terahertz (THz) pulses to nonlinearly excite a set of Raman active modes in centrosymmetric crystals. Using two-dimensional (2D) THz spectroscopy we can investigate photonic and phononic excitation and isolate the dominant and secondary nonlinear excitation pathways. We present a general framework for 2D THz vibrational spectroscopy in solid systems that provides important clarification for the growing new field of nonlinear phononics.

11:30 We-AM-3-2
Cavity Enhanced Third Harmonic Generation From Si:B Pumped With Intense Terahertz Pulses
Fanqi Meng1; Mark D. Thomson1; Bernhard Klug1; Qamar ul-Islam1; Alexej Pashkin2; Harald Schneider2; Hartmut G. Roskos1
1J. W. Goethe-Uni Frankfurt, Germany; 2Helmholtz-Zentrum Dresden-Rossendorf, Germany

we report the third harmonic generation (THG) of the terahertz free electron laser (FEL) pulses from Si:B at cryogenic temperature. The measured χ3 increases as a function of the pumping terahertz intensity. The physical mechanism of the THG is attributed to the free-carrier χ3 nonlinearity due to non-parabolicity of the valance band, where χ3 increases as a function of the carrier density. The free carriers are generated via impact ionization of the frozen boron dopants under irradiation of the FEL pulses. By positioning the Si:B in a one-dimensional photonic crystal (1D PC) cavity, the measured THG intensity increases by about 200 times.

11:45 We-AM-3-3
Terahertz-Induced Electron Emission From A Gold Surface

Shaoxian Li1; Priyo Nugraha1; Ashutosh Sharma2; Csaba Lombosi3; Zoltan Ollmann1; Istvan Marton4; Gyozo Farkas4; Janos Hebling1; Peter Dombi4; Fulop Jozsef5
1Szentágothai Research Centre, University of Pécs, Hungary; 2ELI-ALPS, Hungary; 3University of Pécs, Hungary; 4MTA "Lendület" Ultrafast Nanooptics Group, Wigner Research Centre for Physics, Hungary; 5MTA-PTE High-Field Terahertz Research Group, Hungary

Electron emission was observed at moderate THz peak field strengths below 50 kV/cm. Flipping the polarity of the THz pulses resulted in a significantly different current signal. The electron signal, also measured as function of the THz polarization angle, showed double maxima. In order to compare the photoemission measurement results with the theoretical model, we employed the Fowler-Nordheim (FN) equation along with the classical equation of motion. The enhanced photocurrent with polarity flip (while using the symmetric waveform of THz field) indicates towards rescattering process. In order to investigate the effect of rescattering we numerically solved the time dependent Schrodinger equation to find the emission current probability quantum mechanically.

12:00 We-AM-3-4
Ultrafast Magnetic Recording With Terahertz Light

Ilie Radu1; Mostafa Shalaby2; Martin Hennecke1; Wolfgang Engel1; Clemens KorffSchmising1; Tsukamoto Arata3; Christoph Hauri4; Stefan Eisebitt1
1Max Born institute, Germany; 2Swiss Terahertz LLC, Switzerland; 3College of Science and Technology, Nihon University, Japan; 4Paul Scherrer Institute, Switzerland

We report on the first demonstration of ultrafast magnetisation switching of a spin-ordered material using single-cycle, intense THz pulses at a central frequency of 2 THz.

12:15 We-AM-3-5
Nonlinear THz Field Applications In Free Space

Anastasios Koulouklidis1; Claudia Gollner2; Valentina Shumakova2; Vladimir Fedorov3; Audrius Pugzlys2; Andrius Baltuska2; Stelios Tzortzakis4
1Institute of Electronic Structure and Laser (IESL)/ Foundation for Research and Technology-Hellas (F, Vassilika Vouton, Greece; 2Photonics Institute/TU Wien, Austria; 3Science Program/Texas A&M University at Qatar, Qatar; 4Department of Materials Science and Technology/University of Crete, Greece

Here we demonstrate that intense free space THz fields can nonlinearly induce excitonic photoluminescence in two semiconductors as well as strong cross-phase modulation in an electro-optic crystal.

11:00-12:30 - We-AM-4 - QCL 3 - Room 151

Chairperson: Sukhdeep Dhillon

11:00 We-AM-4-1

Independent Control Of Mode Selection And Power Extraction In Terahertz Quantum Cascade Lasers
Chenren Yu
1; Huan Zhu1; Haiqing Zhu1; Gaolei Chang1; Fangfang Wang1; Jianxin Chen1; Lianhe Li2; A. Giles Davies2; Edmund H. Linfield2; Gangyi Xu1; Li He1
1Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, China; 2School of Electronic and Electrical Engineering, University of Leeds, United Kingdom

We demonstrate novel THz quantum cascade lasers with a gain endowed photonic crystal (PhC) and a grating coupler (GC) formed on each end of the ridge. The PhC acts as a reflection mirror with extremely narrow bandwidth, and the GC enables high radiation efficiency. Such configuration independently controls the mode control and power extraction, and results in stable single mode emission with very high output power. The peak output power reaches to 366 mW at 20K, and remains 224 mW at 77K, measured in pulsed mode.

11:30 We-AM-4-2
THz Quantum Cascade Lasers With Optimized Beam Divergence
Junqi Liu; Jinchuan Zhang; Fengqi Liu; Fangyuan Zhao
Institute of Semiconductors, Chinese Academy of Sciences, China

Single-mode surface-emitting terahertz quantum cascade lasers based on distributed feedback mechanism with high symmetry is presented. By inserting a central Ãfââ?s¬-phase shift or using a non-uniform grating period, an optimized 2-D far-field radiation pattern is obtained. Single-mode emission is achieved with a side-mode suppression ration above 25 dB.

11:45 We-AM-4-3
Dispersion And Ridge Width Effect In Terahertz Quantum Cascade Laser Combs

Wenjian Wan; Kang Zhou; Ziping Li; Xiaoyu Liao; Juncheng Cao; Hua Li
Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, China

The ridge width effect on comb operation of single plasmon waveguide quantum cascade lasers emitting around 4.2 THz is studied by simulation and experiments. The total group velocity dispersion (GVD) is numerically evaluated for 6-mm-long lasers with ridge widths. The simulation reveals that the clamped gain dispersion strongly contributes to the total GVD and the laser with a 150-ÃfŽÃ,¼m-wide ridge shows the flattest total GVD in the lasing range. The optimal ridge width of 150 ÃfŽÃ,¼m for comb operation is also experimentally verified.

12:00 We-AM-4-4
Patch Antenna Microcavities THz Quantum Cascade Lasers
Joel Perez-Urquizo1; Julien Madeo1; Yanko Todorov2; Lianhe Li3; Alexander G. Davies3; Edmund Linfield3; Carlo Sirtori2; Keshav Dani1
1Okinawa Institute of Science and Technology, Japan; 2Ecole Normale Supérieure ENS, Université de Paris, France; 3University of Leeds, United Kingdom

We study the emission of THz quantum cascade lasers (QCLs) designed in arrays of Patch Antenna Microcavities (PAM). The array geometry is an effective strategy to control the losses and to achieve phase locking, allowing for beam shaping and high photon outcoupling efficiency. We demonstrate a 40-fold enhanced emission compared to standard ridge waveguides and a gaussian beam divergence as low as 2° x 2°.

12:15 We-AM-4-5
High-Speed Modulation Of A Terahertz Quantum Cascade Laser Using Coherent Acoustic Phonon Pulses

Aniela Dunn1; Caroline Poyser2; Paul Dean1; Aleksandar Demić1; Alexander Valavanis1; Dragan Indjin1; Mohammed Salih1; Iman Kundu1; Lianhe Li1; Andrey Akimov2; Giles Davies1; Edmund Linfield1; John Cunningham1; Anthony Kent2
1School of Electrical and Electronic Engineering, University of Leeds, United Kingdom; 2School of Physics and Astronomy, University of Nottingham, United Kingdom

We demonstrate a new method for high-speed modulation of terahertz emission and electronic transport of a Ga(Al)As quantum cascade laser using coherent acoustic phonon pulses. The modulation, which is on the order of 6%, can be partially explained by a perturbation-theory analysis. The < 1 ns rise time of the modulation is dominated by parasitic device impedance in our experiment, however, the fast transit of phonons through the QCL heterostructure imply modulation rates > 100 GHz are possible.

11:00-12:30 - We-AM-5 - MMW (active) - Petit Amphi

Chairperson: Chong Han

11:00 We-AM-5-1

Development And Flight Qualification Of The Millimeterwave Receivers For The NASA TROPICS CubeSat Constellation Mission
William Blackwell
MIT Lincoln Laboratory, United States

The Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission was selected by NASA as part of the Earth Venture--Instrument (EVI-3) program and is now in development with planned launch readiness in late 2019. TROPICS comprises a constellation of six CubeSats in three low-Earth low-inclination orbital planes. Each CubeSat will host a high performance millimeterwave radiometer to provide temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapor profiles using three channels near the 183 GHz water vapor absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher resolution water vapor channels), and a single channel at 205 GHz that is more sensitive to precipitation-sized ice particles. NEDTs range from approximately 0.5 to 1.0 K for an 8.333 msec integration time.

11:30 We-AM-5-2
High-Power MM-Wave Frequency Multipliers
Oleg Cojocari; Diego Moro-Melgar; Ion Oprea
ACST GmbH, Germany

A novel approach has been developed on monolithic integration of Schottky diodes with CVD diamond substrate for improved thermal dissipation. This allowed development of mm-wave frequency multipliers with unmatched power-handling capability while maintaining state-of-the-art conversion efficiency. This contribution highlights details of this development and summarizes experimental RF-results of high-power multipliers.

11:45 We-AM-5-3
GaAs Schottky Components For 300 GHz Communication Systems Using A Resonator Impedance Matching Approach

Michael Lancaster1; Cheng Guo1; Jeff Powell1; Hui Wang2; Kai Parow-Souchon2; Peter Huggard2; Yi Wang1
1University of Birmingham, Department of Electronic, Electrical and Systems Engineering, United Kingdom; 2STFC Rutherford Appleton Laboratory, United Kingdom

A interconnection method has been developed to integrate GaAs Schottky diode components with hollow metal waveguides. Instead of using wired or probe impedance matching, an integrated resonator matching circuit has been adopted and a co-design method of active components with waveguide cavity filters developed. The approach transfers most of the matching circuitry from the lossy microstrip to low loss waveguide cavities. It minimises the footprint of the transition and improves the efficiency of the interconnection. This paper reviews the design and test of several building block components for a 300 GHz communications system. A 290-310 GHz single sideband mixer incorporates an integrated waveguide filter to achieve the required image rejection and impedance matching. A 135-150 GHz frequency tripler shows good impedance matching performance with an additional built-in filtering function.

12:00 We-AM-5-4
A 240 GHz Active Multiplier-Based Signal Source For MillimeterWave/Terahertz Applications
Maruf Hossain; Sebastian Boppel; Wolfgang Heinrich; Viktor Krozer
Ferdinand-Braun-Institut, Germany

This paper presents a 240 GHz signal source using a 0.8 Ãfâ?sÃ,µm transferred substrate (TS) InP-HBT technology. The source is based on an active tripler and delivers -3 dBm peak output power at 234 GHz, with a DC consumption of only 50 mW, which corresponds to 0.9 % conversion efficiency. A bandpass filter at the output suppresses all the unwanted harmonics. The tripler achieves more than 50 GHz bandwidth and exhibits very low unwanted harmonics. The core area of the source is only 1.3 x 0.7 mmÃfâ?sÃ,².

12:15 We-AM-5-5
European Schottky-Diode Based Receiver Technology

Oleg Cojocari; Matthias Hoefle; Diego Moro-Melgar; Ion Oprea; Martin Rickes
ACST GmbH, Germany

This contribution summarizes recent achievements of European mm&sub-mm wave receiver technology using Schottky diodes and THz-MICs fabricated by so-called Film-Diode (FD) process. The FD-process has particularly been developed for applications at mm-waves and THz frequencies and targets at ultimate performance at high frequencies. This technology is extensively employed for modern space missions but also finds terrestrial applications.

11:00-12:30 - We-AM-6 - Electronic SC Devices 1 - Room 269

Chairperson: Taiichi Otsuj

11:00 We-AM-6-1

Injection Locking Of Resonant Tunneling Diode Oscillator Using Coherent Terahertz Pulses
Takashi Arikawa1; Jaeyoung Kim2; Toshikazu Mukai2; Naoki Nishigami3; Masayuki Fujita3; Tadao Nagatsuma3; Koichiro Tanaka1
1Kyoto University, Japan; 2ROHM Co., Ltd, Japan; 3Osaka university, Japan

We performed injection locking of a resonant tunneling diode (RTD) oscillator using phase-locked picosecond terahertz pulses. We succeeded in coherent sampling of the terahertz electric field emitted from the RTD.

11:30 We-AM-6-2
Intersubband Polaritons In Triple Barrier Resonant Tunneling Diodes
Benedikt Limbacher1; Martin Kainz1; Sebastian Schönhuber1; Moritz Wenclawiak1; Christian Derntl1; Hermann Detz2; Aaron Andrews3; Goffried Strasser3; Andreas Schwaighofer3; Bernhard Lendl3; Juraj Darmo1; Karl Unterrainer1
1Photonics Institute, TU Wien, Austria; 2CEITEC, Czech Republic; 3TU Wien, Austria

We demonstrate the presence of Intersubband Polaritons in Triple Barrier Resonant Tunneling Diodes. Additionally we investigated the influence of Intersubband Polaritons on the electrical transport and show that the coupling-strength can be modulated electrically.

11:45 We-AM-6-3
Graphene Field-Effect Transistors For Mm-Wave Amplifiers

Andrei Vorobiev1; Marlene Bonmann1; Muhammad Asad1; Xinxin Yang1; Jan Stake1; Luca Banszerus2; Christoph Stampfer2; Martin Otto3; Daniel Neumaier3
1Chalmers University of Technology, Sweden; 2RWTH Aachen University, Germany; 3AMO GmbH, Germany

In this work, we analyze high frequency performance of graphene field-effect transistors (GFETs), applying developed models of drain resistance, carrier velocity and saturation velocity, identify main limitations and propose an approach most promising for further development of the GFETs suitable for advanced mm-wave amplifiers. In particular, it is shown, that the saturation velocity of carriers in the GFETs can be increased up to 5e7 cm/s via encapsulating graphene by hexagonal boron nitride layers, with corresponding increase of extrinsic maximum frequency of oscillation up to 180 GHz at 200 nm gate length

12:00 We-AM-6-4
Wide Bandwidth Terahertz Mixers Based On Graphene FETs

Xinxin Yang1; Andrei Vorobiev1; Kjell Jeppson1; Jan Stake1; Luca Banszerus2; Christoph Stampfer2; Martin Otto3; Daniel Neumaier3
1Chalmers University of Technology, Sweden; 2RWTH Aachen University, Germany; 3AMO GmbH, Germany

In this work, resistive fundamental terahertz mixers with wide RF and IF bandwidths based on graphene field-effect transistors have been demonstrated. With an RF frequency range from 220 GHz to 487 GHz, the estimated values of the 3-dB IF bandwidth are 32 GHz and 56 GHz for mixers with GFET gate lengths of 1.2 ?m and 0.6 ?m, respectively. This is competitive with the performance of mixers based on traditional semiconductor technologies.

12:15 We-AM-6-5
Asymmetric Dual Grating Gate Graphene-based THz Detectors

Juan Antonio Delgado Notario1; Vito Clericò2; Enrique Diez2; Jesus Enrique Velazquez Perez2; Taiichi Otsuji3; Taiichi Otsuji3; Yahya Moubarak Meziani2
1Tohoku University, Japan; 2University of Salamanca, Spain; 3RIEC (Research Institute of Electrical Communication), Japan

We report on detection of terahertz radiation by using Asymmetric dual grating gates graphene-based FET. The device was fabricated with a stack of h-BN/Graphene/h-BN with a back gate as well as an asymmetric dual grating top gates. It was subjected to terahertz radiation at frequencies of 0.15 and 0.3 THz and a clear photocurrent was obtained.

12:30-14:00 - Lunch

14:00-15:15 Parallel sessions We-PM1

14:00-15:15 - We-PM1-1 - THz Plasma 1 - Room 101

Chairperson: Peter Uhd-Jepsen

14:00 We-PM1-1-1
Terahertz Aqueous Photonics And Beyond

Qi Jin1; Yiwen E1; Shenghan Gao1; Liangliang Zhang2; Cunlin Zhang2; Anton Koroliov3; Sergey Kozlov3; Xi-Cheng Zhang1
1University of Rochester, United States; 2Capital Normal University, China; 3ITMO University, Russian Federation

THz wave emission from liquids under intense optical excitation provides a new way to generate intense and broadband THz signals. Here, we show that the use of water lines in place of water films as THz emitters to obtain stronger THz signals. In addition, we observe that the polarity of liquid has a significant influence on the THz wave generation. Besides paving the way to develop intense liquid THz sources, our report could be useful for the further study of laser-liquid interaction.

14:30 We-PM1-1-2
Terahertz Wave Generation From Liquid Nitrogen

Alexander Shkurinov
Moscow, Russian Federation

We present the results of research, on the generation of terahertz (THz) radiation under the action of femtosecond laser pulses on liquid nitrogen (LN). Our experimental results supported by theoretical interpretation, showed that under femtosecond laser radiation, liquid and gas emit THz waves in a very different way. We assume that the mobility of ions and electrons in liquid can play an essential role, forming a timedependent quasi static electric field. We discuss the influence of the phase transition of LN from gas to liquid and then to supercritical fluid on the properties of the THz wave generation.

14:45 We-PM1-1-3
Double Pulse Excitation For Enhancing THz Generation In Liquid Jets

Evgenia Ponomareva1; Sergei Putilin1; Anastasia Gendrina1; Semen Smirnov2; Anton Tcypkin1; Yiwen E3; Sergei Kozlov1; Xi-Cheng Zhang3
1ITMO University, Russian Federation; 2Aston University, United Kingdom; 3University of Rochester, United States

We implement a double-pump technique to enhance THz energy generated in liquid jets. The dependence of the THz emission enhancement efficiency on the temporal delay between two collinear optical pulses is experimentally and theoretically investigated. To understand the physics of the process, we compare the cases of 200 fs and 300 fs pump pulses and reveal the advantage of using a pulse of optimal for a specific jet thickness duration for more efficient enhancement. We assume that in addition to the effective method of strong THz generation, double-pump can be a method of measuring the plasma channel lifetime.

15:00 We-PM1-1-4
Flexible Control Of Broadband Terahertz Radiations From Laser Plasmas

Zhelin Zhang1; Yanping Chen2
1Tsung-Dao Lee Institute, China; 2Key Laboratory for Laser Plasmas, Shanghai Jiao Tong University, China

Based on theoretical and experimental studies, we demonstrate that the two-color laser scheme in gas plasma can provide effective control of broadband terahertz waves, including their waveforms and polarization states.

14:00-15:15 - We-PM1-2 - PC Devices 2 - Room 162

Chairperson: Masahiro Asada

14:00 We-PM1-2-1

Milliwatt-Class MHz Repetition-Rate THz Source Driven by A Sub-100 Fs High Power Thin-Disk Laser
Frank Meyer; Negar Hekmat; Tim Vogel; Alan Omar; Samira Mansourzadeh; Felix Fobbe; Martin Hoffmann; Yicheng Wang; Clara Saraceno
Ruhr-University Bochum, Germany

We demonstrate optical rectification in GaP crystals driven by a 100 W-class thin-disk oscillator, nonlinearly compressed to sub 100 fs in a multi-pass cell. We measure a power of 1.35 mW, which is the highest average power of a table- top single-cycle THz source at MHz repetition rate so far.

14:30 We-PM1-2-2
Interdigitated Photoconductive Switches For Terahertz Pulses Emission With Electrical Control Of Polarization

Kenneth Maussang1; Jacques Hawecker2; José Palomo2; Juliette Mangeney2; Sukhdeep S. Dhillon2; Jérôme Tignon2
1Université de Montpellier, France; 2Laboratoire de Physique de l'ENS - ENS, Université PSL, CNRS, Sorbonne Université, Université Paris, France

Photoconductive switches are widely used for emission and/or detection of terahertz pulses, linearly polarized in a direction fixed by electrodes' geometry. In this work, innovative designs of photoconductive switches are demonstrated and characterized, providing full electrical control on the direction of polarization of the emitted field. Based on an interdigitated scalable geometry, it might be used either for emission or detection, allows fast polarization modulation and polarimetry measurements with a large area receiver. Degree of polarization better than 98% has been measured and investigated numerically. It opens the field of precision terahertz polarimetry.

14:45 We-PM1-2-3
Scalable Large-Area Terahertz Emitters With Improved Electrode Design

Abhishek Singh; Malte Welsch; Stephan Winnerl; Manfred Helm; Harald Schneider
Helmholtz-Zentrum Dresden-Rossendorf, Germany

We have systematically investigated the influence of electrode parameters on the emission efficiency of scalable large-area photoconductive THz emitters. We identify two contributions to THz emission, originating from the photoexcited carriers in the semiconductor and from the interdigitated metal electrodes acting as dipole antennae, respectively. Both contributions are optimized for maximum THz emission efficiency by varying the gap and stripe widths of the interdigitated metal electrodes. Using this approach we achieve a 50% improvement of the radiated THz electric field as compared to electrodes with equal stripe and gap widths.

15:00 We-PM1-2-4
Cavity Based THz Photoconductive Switch: Milliwatt Average Powers

Jacques Hawecker1; Kenneth Maussang1; José Palomo1; Rafaelle Colombelli2; Isabelle Sagnes2; Juliette Mangeney1; jérome Tignon1; Sukhdeep Dhillon1
1Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne University, France; 2Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris Sud, Université Paris-Saclay, C2N M, France

Reaching milliwatt average powers and room temperature operation for THz sources has become the key challenge for the uptake of THz applications that require real-time imaging. This criteria remains extremely challenging. By placing a photoconductive switch within a quasi-resonant cavity, we are able to show average power around 2mW which is an important development towards room temperature THz imaging.

14:00-15:15 - We-PM1-3 - NLO Generation 1 - Amphi Lavoisier

Chairperson: Harmut Roskos

14:00 We-PM1-3-1

Low Noise And High Gain Terahertz Parametric Amplifier
Kosuke Murate; Hikaru Sakai; Yunzhuo Guo; Kodo Kawase
Nagoya University, Japan

In this study, we demonstrated a low-noise, high-gain terahertz (THz) parametric amplifier (TPA). The TPA is divided into two parts: a preamplifier and a main amplifier. In this configuration, wavelength conversion to near-infrared (NIR) light is performed by the preamplifier. The NIR light has different generation angles for each wavelength to satisfy the phase-matching conditions; thus, broadband noise can be spatially removed using an iris. Converting the THz wave again in the main amplifier, an improvement in amplification is realized, while reducing noise. These improvements allowed the amplification gain to reach 98 dB at 506 zJ input at 0.79 THz.

14:30 We-PM1-3-2
Generation Of THz Vortex Beam By Infrared Vector Beam Rectification

Jérôme Degert; Ali Al Dhaybi; Etienne Brasselet; Emmanuel Abraham; Eric Freysz
Université de Bordeaux - LOMA, France

We report on the conversion of an infrared vector beam into THz vortex beams using a ZnTe cubic crystal. We provide a theoretical analysis demonstrating how an infrared vector beam with the azimuthal order l can be transformed into a THz beam endowed with an orbital angular moment content that consists of optical vortices with topological charge +2l or -2l. Experimentally, quasi-monochromatic THz vortex beams with topological charges +2 and -2 are produced and characterized both in amplitude and phase using real-time two-dimensional imaging of the terahertz electric field.

14:45 We-PM1-3-3
Efficient Terahertz Generation And Detection Using CdTe Crystal Pumped By Ultrafast Ytterbium Laser

Xavier Ropagnol1; Mizuho Matoba2; Joel-Edouard Nkeck3; François Blanchard3; Elchin Isgandarov1; Junji Yumoto2; Tsuneyuki Ozaki1
1INRS-EMT, INRS-EMT, Canada; 2The university of Tokyo, Japan; 3ÉTS, Canada

In this work, we study terahertz (THz) generation and detection from CdTe crystal pumped by an Ytterbium (Yb) laser at 1.045 Ã,µm wavelength. We compare the performances of THz emission and detection of CdTe crystals to those of GaP crystals and show 50% higher efficiency for detection and 5 times higher efficiency for generation of THz waves from the CdTe crystal. We demonstrate that the generation process is optical rectification from the bulk crystal while the detection process is based on the Pockel effect. We believe this work shows that CdTe crystal could be used as detector and especially as a source for THz time domain spectroscopy.

15:00 We-PM1-3-4
Evidence For THz Superradiance In Optically-Pumped Quantum-Dot Arrays

W-D. Zhang1; E. Brown1; A. Mingardi2; R. Mirin3; N Jahed4; D. Saeedkia4
1Department of Physics, THz labs, Wright State University, United States; 2Departments of Physics and Electrical En, Wright State University, United States; 3Applied Physics Division, National Institute of Standards and Technology, United States; 4TeTechS, Canada

We present the first experimental results of THz oscillatory radiation from quantum dot arrays in GaAs pumped by 1550-nm femtosecond pulses. A record of ~117 μW THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%.

14:00-15:15 - We-PM1-4 - QCL 4 - Room 151

Chairperson: Miriam Vitiello

14:00 We-PM1-4-1

Long Wavelength (λ = 10 - 18 μM) Mid-IR Quantum Cascade Lasers Operating In A Continuous Wave At Room Temperature
Roland Teissier; Hadrien Philip; Zeineb Loghmari; Michael Bahriz; Alexei Baranov; Franziska Barho
University of Montpellier, France

We report a study of quantum cascade lasers (QCL), made of InAs and AlSb, operating in the long wavelength mid-infrared range. Lasers based on a design with slightly diagonal intersubband transitions demonstrated improved performances as compared to the previously reported devices employing a vertical scheme. The fabricated lasers operated in the CW regime at 40°C up to a wavelength of 18 μm.

14:30 We-PM1-4-2
Self-starting Harmonic Emission And Active Harmonic Modelocking In THz QCLs

Valentino Pistore1; Feihu Wang1; Michael Riesch2; Hanond Nong1; Pierre-Baptiste Vigneron3; Raffaele Colombelli3; Olivier Parillaud4; Christian Jirauschek2; Juliette Mangeney1; Jerome Tignon1; Sukhdeep Dhillon1
1LPENS, France; 2Technical University of Munich, Germany; 3Universite Paris-Sud, France; 4III-V Lab, France

In laser technology, harmonic modelocking is usually employed to attain higher repetition rates that is associated with lower noise systems. Despite the favourable dynamics of THz QCLs, harmonic active modelocking has not been experimentally demonstrated yet. In this work, we present the results of active modelocking experiments performed at the fundamental and second harmonic on a 6mm double metal THz QCL. We will also show that in certain cases, QCLs can spontaneously attain second harmonic emission without an active modulation, i.e. self-starting harmonic behaviour.

14:45 We-PM1-4-3
Compact Real-Time Terahertz Spectroscopy Based On Quantum Cascade Lasers

Hua Li; Ziping Li; Wenjian Wan; Kang Zhou; Juncheng Cao
Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, China

We demonstrate the most compact terahertz multiheterodyne dual-comb spectroscopy using two quantum cascade lasers (QCLs) without a need of additional fast detectors. With only ~270 nW terahertz power coupled into a terahertz QCL detector comb (no optics for alignment), the down-converted dual-comb spectra are successfully obtained in real-time at different carrier frequencies. To prove the spectroscopic ability, we further demonstrate that the compact dual-comb system can be used to calibrate the relative humidity in the air and to measure the transmission of samples. Due to the small optical coupling aperture (150 μm), it is also potential to use the dual-comb technique for terahertz imaging.

15:00 We-PM1-4-4
Dynamics Of Optically Mutual-injected Terahertz Quantum Cascade Lasers

Weidong Chu1; Yuanyuan Li1; Ning Yang1; Yan Xie2; Yingxin Wang2; Ziran Zhao2; Jialin Sun2; Lianhe Li3
1Institute of Applied Physics and Computational Mathematics, China; 2Tsinghua University, China; 3Leeds University, United Kingdom

Based on the rate equation model, we study the phase locking and self-mixing properties of optically mutual-injected terahertz quantum cascade lasers. Within the phase-locked range, the laser array works steadily at the same frequency, and the electric field amplitudes are stable. Outside the phase-locked range, the instantaneous frequencies and electric field amplitudes oscillate with time. When the array works in the phase-locked range, simulation with a moving target shows that self-mixing signals can be observed from each laser.

14:00-15:15 - We-PM1-5 - MMW (passive) - Petit Amphi

Chairperson: Raffaele Colombelli

14:00 We-PM1-5-1

Dual-Band Leaky-Wave Lens Antenna For Submillimeter-Wave Heterodyne Instruments
Sjoerd Bosma1; Maria Alonso-delPino2; Darwin Blanco1; Cecile Jung-Kubiak2; Nuria Llombart1
1Delft University of Technology, Netherlands; 2Jet Propulsion Laboratory, United States

In this contribution, we propose an antenna for a dual-band focal plane array (FPA) heterodyne receiver at 210-240 GHz and 500-580 GHz to perform cometary observations. The proposed antenna is composed of a fused silica lens fed by a leaky wave waveguide feed. The dual-band leaky wave feed is based on a single-layer Frequency Selective Surface (FSS) with a transformer layer which allows to have a quasi-optical system that achieves a footprint of the field of view with overlapped beams and equal beamwidths for both frequency bands. A single pixel antenna prototype is currently being developed.

14:30 We-PM1-5-2
A Compact Butler Matrix Design Based On Metallic Nano Wire Filled Membrane Technology And Tunable Phase Shifter At 160GHz

Dongwei Wang1; Matthias Jost1; Matthias Nickel1; Roland Reese1; Gustavo Pamplona Rehder2; Serrano Ariana L.C.2; Ferrari Philippe3; Rolf Jakoby1; Holger Maune1
1TU Darmstadt, Germany; 2Universidade de São Paulo, Brazil; 3UJF, France

This paper presents the design of a planar miniaturized 4x4 Butler matrix, with implementation of 4 tunable 135° delay line phase shifters for a 160 GHz application. The Butler matrix and phase shifters are both realized with a metallic nanowire filled alumina membrane (NaM) technology, using a slow-wave microstrip line to miniaturize the size and where tunability is achieved by filling in a microwave liquid crystal. Comparing with commonly used corporate feed network, the simulation results show such a Butler matrix with 135°-phase shifters has less insertion loss and reduced size.

14:45 We-PM1-5-3
High Performance On-Chip Array Antenna Based On Metasurface Feeding Structure For Terahertz Integrated Circuits

Mohammad Alibakhshikenari1; Bal S. Virdee2; Chan H. See3; Raed A. Abd-Alhameed4; Ernesto Limiti5
1Electronic Engineering Department, University of Rome, Italy; 2London Metropolitan University, Center for Communications Technology & Mathematics, School of Computing & Digital Media, United Kingdom; 3Edinburgh Napier University, School of Eng. & the Built Environment, United Kingdom; 4University of Bradford, School of Electrical Eng. & Computer Science, United Kingdom; 5University of Rome "Tor Vergata", Electronic Engineering Department, Italy

A novel on-chip array antenna with high-performances is investigated which is based on CMOS-20um Silicon technology for operation over 0.6-0.65THz. The proposed array structure is constructed on three layers composed of Silicon-Ground-Silicon layers. Two antennas are implemented on the top layer, where each antenna is constituted from three sub-antennas. The sub-antennas are constructed from interconnected dual-rings. Also, they are interconnected to each other. This approach enlarges the effective aperture area of the array. Surface-waves and substrate losses in the structure are suppressed with via-holes inserted through the three layers and implemented between the radiation elements. To excite the structure, a novel feeding mechanism is used comprising open-circuited microstrip lines, which couple electromagnetic energy from the bottom layer to the antennas through metasurface slot-lines in the middle ground-plane layer. The results show the proposed on-chip antenna array has an average radiation gain, efficiency, and isolation of 7.62dBi, 32.67%, and -30dB, respectively.

15:00 We-PM1-5-4
Microfabrication And Study Of Planar Slow-Wave Structures For Low-Voltage V-band And W-band Vacuum Tubes

Andrey Starodubov1; Nikita Ryskin1; Andrey Rozhnev1; Anton Pavlov2; Alexey Serdobintsev2; Roman Torgashov1; Victor Galushka1; Ilya Kozhevnikov2; Igor Bahteev3; Giacomo Ulisse4; Viktor Krozer4
1Saratov Branch, Institute of Radio Engineering and Electronics, RAS, Russian Federation; 2Saratov State University, Russian Federation; 3Central Institute of Measurement Equipment (JSC CIME), Russian Federation; 4Goethe University Frankfurt am Main, Germany

We consider further development of our original technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS). The technology is based on magnetron sputtering and laser ablation methods. V-band (50-75 GHz) and W-band (75-110 GHz) SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. We have also carried out preparations and preliminary technological steps for the microfabrication of D-band (110-170 GHz) planar microstrip slow-wave structures.

14:00-15:15 - We-PM1-6 - Microscopy - Room 269

Chairperson: Vincent Wallace

14:00 We-PM1-6-1

Imaging Biological Samples Using Far- And Near-Filed THz Microscopy
Huabin Wang
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, China

Both the far-field and near-field THz imaging techniques have been demonstrated in the detection of biological samples, from which it is reasonable to believe that THz imaging techniques are holding a bright future in biomedical and biological fields.

14:30 We-PM1-6-2
Sub-wavelength THz Imaging Through Optical Rectification

Gizem Soylu1; Emilie Hérault1; Fredrik Laurell2; Benoit Boulanger3; Jean-Louis Coutaz1
1Univ. Grenoble Alpes, Univ. Savoie Mont-Blanc, UMR CNRS 5130, Grenoble INP, IMEP-LAHC, France; 2Department of Applied Physics, KTH, Royal Institute of Technology, Sweden; 3University Grenoble Alpes, Institute Néel, France

Sub-wavelength THz imaging has previously been demonstrated by the optical rectification method, i.e. generating THz waves in the sample [1]. We have rendered the initial experimental setup more practical by using a simple fs laser oscillator and an efficient photo-conducting detector. We thus recorded images, at different THz frequencies with a 41-µm lateral resolution, of a sample made of ZnTe grains, and generated THz peak magnitudes with a 33 µm and 12 µm lateral resolution of a periodically poled KTP crystal.

14:45 We-PM1-6-3
Anisotropic Terahertz Microscopy Of Protein Collective Vibrations: Crystal Symmetry And Hydration Dependence

Jeffrey McKinney; Yanting Deng; Akansha Sharma; Deepu George; Andrea Markelz
Buffalo, United States

A stationary sample anisotropic terahertz microscopy technique is used to characterize the intramolecular vibrations for lysozyme. Tetragonal and triclinic crystals are compared. We find excellent reproducibility within a single crystal symmetry group. Several resonant bands are present for both symmetry groups, indicating they originate with the intramolecular vibrations and not crystal lattice phonons. Bands become more pronounced and higher frequency resonant bands begin to emerge with slight dehydration.

15:00 We-PM1-6-4
Observation Of Bi2Te3/Te Striped Structures Using A Laser Terahertz Emission Microscope

Fumikazu Murakami1; Kazunori Serita1; Hironaru Murakami1; Rea Dalipi1; Augustine Urbas2; M. Buza3; A. Materna3; Dorota Pawlak3; Masayoshi Tonouchi1; Iwao Kawayama1
1Institution of Laser Engineering, Japan; 2Materials and Manufacturing Directorate, United States; 3Institute of Electronic Materials Technology, Poland

We observed waveforms and images of THz radiation from Bi2Te3/Te striped structures with laser terahertz emission microscope (LTEM). The results indicate that THz emission from Te is stronger than from Bi2Te3 and the amplitude of THz with polarization in parallel to the striped lines is larger than that in perpendicular.

15:15-15:45 - Coffee Break

15:45-17:00 Parallel sessions We-PM2

15:45-17:00 - We-PM2-1 - THz Plasma 2 - Room 101

Chairperson: Frank Hegmann

15:45 We-PM2-1-1
Highly Efficient Broadband THz Generation From Mid-IR Laser-Driven Plasma

Claudia Gollner1; Anastasios D. Koulouklidis2; Valentina Shumakova1; Vladimir Yu Fedorov3; Audrius Pugzlys1; Andrius Baltuska1; Stelios Tzortzakis4
1Photonics Institute/ TU Wien, Austria; 2Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology - Hellas, Greece; 3P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Russian Federation; 4Science Program, Texas A&M University at Qatar, Qatar

We report on THz generation from two-color laser filaments, driven by intense Mid-IR pulses centered at 3.9 µm. We demonstrate generation of THz pulses with a spectral bandwidth of 15 THz, extraordinary conversion efficiency of 2.34% and remarkably high energy of 0.185 mJ.

16:15 We-PM2-1-2
Conical Vs Gaussian Terahertz Emission From Two-Color Laser-Induced Air Plasma Filaments

Christian Sørensen1; Esben Skovsen2; Jérôme Degert3; Marc Tondusson3; Eric Freysz3; Emmanuel Abraham3
1Aalborg University, Department of Materials and Production, Denmark; 2Aalborg University, Denmark; 3CNRS LOMA, UMR 5798, Université de Bordeaux, France

We demonstrate that terahertz generation in a two-color laser filament can exhibit conical or Gaussian far-field distribution depending on the experimental conditions. By measuring the spatial distribution of the THz electric field in the 0-3 THz spectral range, we have shown that the conical emission is likely due to photo-induced carriers in the silicon filter used to block the remaining pump laser pulses. However, the terahertz generation can retrieve a Gaussian spatial distribution by replacing the silicon filter by a ceramic one in which the photo-excitation of charge carrier does not occur.

16:30 We-PM2-1-3
Filamentation-assisted MicroJ THz Generation By 2-TW Laser Pulses In A Low-pressure Gas

Maxim Nazarov1; Alexander Mitrofanov2; Dmitry Sidorov-Biryukov2; Mikhail Chasсhin2; Maxime Bernier3; Alexey Zheltikov4; Vladislav Panchenko2
1NRC "Kurchatov institute", NRC "Kurchatov institute", Russian Federation; 2Kurchatov institute, Russian Federation; 3Institut de Microélectronique, Electromagnétisme et Photonique, IMEP-LAHC (UMR 5130), France; 4ILC and Physics Department M.V. Lomonosov Moscow State University, Russian Federation

A 2-TW, 30-fs, 800-nm laser radiation is combined with its second harmonic to yield a two-color filament in a loose-focusing geometry inside a low-pressure gas cell. With multiple filamentation and excessive ionization avoided in our experiments through an appropriate choice of the sort and the pressure of the gas, as well as focusing conditions, this filament provides a bright source of terahertz pulses, at least with microjoule-level, for part of the spectrum below 10 THz. Hundred-fold increase of THz yield is observed for 1-50 mbar gas pressure in comparison with ambient case. This THz output is focusable, as our experiments show, to field intensities high enough to induce a 16% transmission increase of a silicon wafer, indicating THz-field strengths up to 0.3 MV/cm in the beam-waist region.

16:45 We-PM2-1-4
New Approach To THz Pulse Generation In Plasma Created By High-Intensity Laser Field

Anna Bogatskaya; Alexander Popov; Ekaterina Volkova
Moscow State University, Russian Federation

We propose new approach to the problem of generation of terahertz radiation in nonequilibrium plasma channels created by high-intensity laser radiation in gases. Key idea of the proposed approach lies in implementing additional amplification to the laser-induced generated THz pulse due to the specific properties of nonequilibrium plasma channel. We perform a self-consistent analysis of the processes of terahertz pulse formation by four-wave mixing process as well as by relaxation of residual low-frequency currents and it further propagation and amplification in a nonequilibrium plasma medium in a wakefield of the laser pulse. Optimal parameters for the pump laser pulse and gaseous medium are found for the most efficient conversion of its energy into terahertz pulse.

15:45-17:00- We-PM2-2 - Applications 2 - Room 162

Chairperson: Withawat Withayachimnankul

15:45 We-PM2-2-1

Online Measurement Of Tire Ply Balance
Irl Duling; Jeffrey White
TeraMetrix, United States

A critical measurement in the manufacture of tires is the ply balance. This is the amount of rubber above and below the cord. In this talk we will present the online measurement of tire ply balance for both textile and steel cords. A combination of x-ray and nuclear gauges can accomplish this measurement for steel cord, but terahertz is the first technology that can measure balance for textile cord. This is also the first of many possible applications of pulsed terahertz within the tire industry.

16:15 We-PM2-2-2
Highly Integrated Submillimeter-Wave Spectrometer For CubeSats
Goutam Chattopadhyay; Adrian Tang; Maria Alonso-delPino; Cecile Jung-Kubiak; Jacob Kooi; Jose Siles; Choonsup Lee
NASA Jet Propulsion Laboratory, United States

We are developing a highly integrated submillimeter-wave spectrometer suitable for CubeSat and SmallSat platforms. Since the available space and DC power on a CubeSats is limited and the instrument has to be light weight, traditional methods of assembling submillimeter-wave instruments are not suitable on these platforms. In this paper we show how we are addressing all these by using low-profile antennas, MEMS calibration switch, and CMOS spectrometers

16:30 We-PM2-2-3
Investigating The Influence Of A Compact's Geometry On Its Pore Structure And Optical Properties Using Terahertz Spectroscopy

Prince Bawuah1; Runqiao Dong1; Mohammed Al-Sharabi1; Daniel Markl2; Axel Zeitler1
1University of Cambridge, United Kingdom; 2University of Strathclyde, Institute of Pharmacy and Biomedical, United Kingdom

In this study, terahertz time domain spectroscopy (THz-TDS) is used to analyze how the geometry of a compact affects its pore structure (pore shape and orientation). By using flat-faced and biconvex compacts, it was evident from our analysis that pores tend to assume specific shapes and orientations based on the compact's geometry and this was found to significantly affect the extracted optical properties of samples prepared by mixing a material with polyethylene (PE) or polytetrafluoroethylene (PTFE) ethylene as diluent and subsequent compaction. However, such sensitivity to the pore properties opens a number of industrial applications such as for quality testing of pharmaceutical tablets.

16:45 We-PM2-2-4
On-site Inspection Of Conservation Works Using THz TDS

Kirsti Krügener1; Jan Ornik2; Maximilian Schneider2; Alexander Jäckel2; Enrique Castro-Camus3; Martin Koch2; Wolfgang Viöl1
1HAWK University of Applied Sciences and Arts, Germany; 2Philipps-Universität Marburg, Germany; 3Centro de Investigaciones en Óptica, A.C., Mexico

After conservation works were done, we performed on-site THz TDS measurements of Roman paintings on the facade of Roman Imperial Throne Room in Trier and compared them to in-lab studies on mockup samples. Results indicate that an intermediate layer of cyclododecan sublimated.

15:45-17:00 - We-PM2-3 - NLO Generation 2 - Amphi Lavoisier

Chairperson: Jean-François Roux

15:45 We-PM2-3-1

Improving The Efficiency Of Cherenkov-Type Terahertz Generation In LiNbO3 By Using Longer Wavelength Optical Pump
Sergey Bodrov1; Igor Ilyakov2; Boris Shishkin2; Michael Bakunov1
1University of Nizhny Novgorod, Russian Federation; 2Institute of Applied Physics of the Russian Academy of Sciences, Russian Federation

Terahertz generation by optical rectification of femtosecond laser pulses in a structure comprising a 40 µm thick LiNbO3 waveguide layer and an output Si prism has been investigated for different (800-2400 nm) central wavelengths of the optical pump. An increase in the optical-to-terahertz conversion efficiency for longer pump wavelengths has been obtained and attributed to higher saturation pump energy. In particular, record high conversion efficiency of 0.6 % has been achieved for µJ-level pump at 2100 nm.

16:15 We-PM2-3-2
Optical-to-THz Frequency Down-Conversion Utilizing Two-Dimensional Plasmons

Soya Manabe; Taiichi Otsuji; Akira Satou
Tohoku University, Japan

We theoretically study the carrier frequency down-conversion from optical signals to terahertz signals utilizing two-dimensional plasmons in an InGaAs-channel high-electron-mobility transistor (InGaAs-HEMT). We demonstrate that the down-conversion can be implemented by the so-called photonic double-mixing functionality in the HEMT utilizing the plasmonic hydrodynamic nonlinearities and that the double-mixing conversion gain can be enhanced by orders of magnitude with help of the plasmon-resonance effect.

16:30 We-PM2-3-3
Photonic Upconversion For THz Radiometry

Gabriel Santamaria Botello; Kerlos Atia Abdalmalak; Daniel Segovia Vargas; Luis Enrique García Muñoz
Universidad Carlos III de Madrid, Spain

We analyze the feasibility of upconverting mm-wave and THz radiation to the optical domain for high sensitivity radiometry with no need of cryogenic operation. The upconversion takes place via electro-optic modulation in high-Q whispering-gallery resonators. Theoretical noise results show that room-temperature upconversion schemes can achieve sensitivity values comparable to those of cooled state-of-the-art mm-wave LNAs provided that photon conversion efficiencies above 1% are accomplished.

16:45 We-PM2-3-4
Efficient Broadband Terahertz Generation From Organic Crystal BNA Using Near Infrared Pump

Hang Zhao1; Tong Wu2; Yong Tan2; Gunther Steinfeld3; Yan Zhang4; Cunlin Zhang4; Liangliang Zhang2; Mostafa Shalaby4
1Beijing Institute of Technology, China; 2Beijing Institute of Technology, China; 3Swiss Terahertz Research-Zurich, Switzerland; 4Capital Normal University, China

we have shown that BNA is potentially a suitable THz emitter for intense source upscaling using high energy NIR lasers. The obtained spectral contents extend up to 8 THz and the conversion efficiency is 0.8%. We did not observe saturation of conversion efficiency or effect of nonlinear absorption at the maximum fluence used in our experiment.

15:45-17:00 - We-PM2-4 - FEL 1 - Room 151

Chairperson: John Jelonnek

15:45 We-PM2-4-1

Ultrafast High-Field THz Beamline At X-ray FEL
Nikola Stojanovic; Rui Pan; Ekaterina Zapolnova
Deutsches Elektronen-Synchrotron (DESY), Germany

THz sources at FLASH utilize spent electron beam from an soft X-ray FEL to generate very intense (up to 150µJ), tunable frequency (1-300THz) and ultrafast narrowband (~10%) THz pulses, which are naturally synchronized to soft X-ray pulses. This unique combination allows for wide range of element specific pump-probe experiments in physics, material science and biology. Here we discuss the unique features of the FLASH THz pulses and the accelerator source that bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles.

16:15 We-PM2-4-2
Powerful Spatially-Extended Cherenkov Masers For Pumping Systems Of Compton FELs

Nikolai Peskov; Edward Abubakirov; Andrey Denisenko; Naum Ginzburg; Andrey Savilov; Alexander Vikharev; Vladislav Zaslavsky
Institute of Applied Physics RAS, Russian Federation

Conception of Compton-type FELs is under development currently at IAP RAS (N.Novgorod). This concept is aimed at reducing energy of a driving relativistic electron beam and thereby increasing efficiency of the electron-wave interaction in FEL, as well as achieving relative compactness of the generator. The basis of this concept is RF-undulators of a new type - the so-called "flying" undulators. The report is devoted to design parameters of the Cherenkov maser intended for powering the RF-undulator of such type in the Ka-band, results of its simulation and initial experimental studies. In order to achieve the required sub-gigawatt power level of the pumping wave in a strongly oversized oscillator, we exploit the original idea of using two-dimensional distributed feedback implemented in the 2D doubly-periodical slow-wave structures.

16:30 We-PM2-4-3
Regime Of Multi-Stage Trapping In Free Electron Lasers

Andrey Savilov; Yulia Oparina; Nikolai Peskov
Institute of Applied Physics RAS, Russian Federation

We describe two different ways of the use of the regime of "multi-stage" trapping in Free-Electron Laser. First, this regime can be a way for efficiency enhancement of FELs operating in the SASE regime. Second, multi-stage amplification of a single-frequency RF signal can lead to an effective cooling of the operating electron beam.

16:45 We-PM2-4-4
Accelerator-based Tunable THz Source For Pump-and-probe Experiments At The European X-ray Free-Electron Laser Facility

Hamed Shaker1; Mikhail Krasilnikov1; Prach Boonpornprasert1; Xiangkun Li1; Georgi Georgiev1; Axel Brachmann2; Ye Chen1; James Good1; Matthias Gross1; Holger Huck1; Igor Isaev1; Christian Koschitzki1; Gerald Koss1; Shankar Lal1; Osip Lishilin1; Gregor Loisch1; David David Melkumyan1; Raffael Niemczyk1; Heinz-Dieter Nuhn2; Anne Oppelt1; Sebastian Philipp1; Mario Pohl1; Houjun Qian1; Evgeny Schneidmiller1; Guan Shu1; Joerg Schultze1; Frank Stephan1; Grygorii Vashchenko1; Mikhail Yurkov1
1DESY, Germany; 2SLAC, United States

There is a high demand for intense THz sources since "many excitation mechanisms of matter resonate in the terahertz regime" especially for condensed matters. "Accelerator-based THz sources provide the wide tunability together with high intensity and repetition rates beyond 100 kHz, that will enable broad application at the European XFEL to the most interesting scientific problems in the field" [1]. Supported by European XFEL a proof of principle study is started at the Photo-Injector Test Facility located at DESY in Zeuthen site (PITZ). Since PITZ and European XFEL electron sources are identical the X-ray and THz radiation can be produced with identical bunch train structure so that for every X-ray pulse a corresponding THz pulse can be provided for the pump-and-probe experiments.

15:45-17:00 - We-PM2-5 - Metamaterials 4 - Petit Amphi

Chairperson: Fritz Keilmann

15:45 We-PM2-5-1

Sensitive Biomolecule Sensing And Imaging Platforms Using Terahertz Metamaterials
Minah Seo; Sang-Hun Lee
Korea Institute of Science and Technology, Republic of Korea

We developed terahertz time-domain sensing and imaging platforms for highly sensitive and selective molecule detection in very low concentration. Highly sensitive sensing performance was obtained by various designs of nanoscale metal resonators and their lateral pattern array. Small quantity of target biomolecules was detectably assisted by resonance behavior and huge terahertz field enhancement at the near-field regime. Further studies with large area metamaterial sensing chips represented great promise as a two-dimensional imaging sensor with high contrast and efficient discrimination.

16:15 We-PM2-5-2
A Polarization Insensitive Metasurface For Terahertz Biosensing Applications

Zheng Zhu; Jun Zhou; Lin Zhou; Yanshun Zheng; Jun Wang
University of Electronic Science and Technology of China, China

In this work, a polarization insensitive metasurface operating at the low-frequency edge of the terahertz (THz) band was designed, simulated, optimized, micro-fabricated, and finally tested by the THz time-domain spectroscopy (TDS) system. The simulation and experimental results agree with each other very well. The conclusions show the advantage of this metasurface for THz biosensing applications.

16:30 We-PM2-5-3
Labyrinth Metasurface-based Devices For High-sensitivity Thin Film Sensing

Irati Jauregui-Lopez1; Pablo Rodriguez-Ulibarri1; Aitor Urrutia1; Sergei A. Kuznetsov2; Miguel Beruete1
1Universidad Pública de Navarra, Dept. Ing. Eléctrica, Electrónica y de Comunicación. Spain; 2Rzhanov Institute of Semiconductor Physics SB RAS, Russia, Spain

In this work, two labyrinth metasurfaces with inductive and capacitive behavior operating in the range of the Terahertz (THz) are presented. The high concentration of electric field in these structures led to excellent results for the use of the devices as thin-film sensors. Numerical and experimental studies have been carried out, with excellent sensitivity and Figure of Merit (FOM) results enhancing dramatically those found in the literature. Due to its great behavior, the use of these thin-film sensors could be extended to perform biological sensing in the future.

16:45 We-PM2-5-4
Terahertz Sensing Of Methyl Chlorpyrifos Using Carbon Nanotube Metamaterials

Ruiqian Wang; Wendao Xu; Lijuan Xie; Yibin Ying
Zhejiang University, China

The results demonstrate that sensitivity is greatly improved using carbon nanotube terahertz metamaterials, which is lower than the World Health Organization's provisional guideline limit for methyl chlorpyrifos in vegetables.

15:45-17:00 - We-PM2-6 - Near-field 1 - Room 269


15:45 We-PM2-6-1

Mid-infrared Nano-tomography Of Topological Insulator Surfaces
Fabian Mooshammer1; Fabian Sandner1; Markus A. Huber1; Martin Zizlsperger1; Helena Weigand1; Markus Plankl1; Christian Weyrich2; Martin Lanius2; Joern Kampmeier2; Gregor Mussler2; Detlev Gruetzmacher2; Jessica Boland1; Tyler L. Cocker3; Rupert Huber1
1University of Regensburg, Germany; 2Peter Gruenberg Institut 9, Germany; 3Michigan State University, United States

The local dielectric function of a few-nm-thick surface layer on a three-dimensional topological insulator is directly retrieved by mid-infrared nano-tomography and suggests the coexistence of a massive electron gas and the topologically protected surface states.

16:15 We-PM2-6-2
Electrically Tunable THz Near-field Nano-imaging And Spectrum Of Split Graphene Ribbon

Zhuocheng Zhang; Min Hu; Yueying Wang; Tianyu Zhang; Xingxing Xu; Sen Gong; Tao Zhao; Shenggang Liu
University of Electronic Science and Technology of China, China

We demonstrate the THz near-field nano-imaging and spectrum of split graphene ribbon utilizing THz scattering near-field optical microscopy (SNOM). Here, we obtain different near-field imaging when we apply different voltages to the device. Furthermore, we investigate THz near-field and far-field spectrum of this structure. We find that only the near-field signal of split graphene ribbon is tuned electrically, rather than far-field signal. The phenomena reveal the THz near-field and far-field properties of graphene with different Fermi level, which is of great significance to learn characteristics of graphene in THz band.

16:30 We-PM2-6-3
Near-field Spectrum Analysis Of TDS S-SNOM

Yueying Wang; Min Hu; Sen Gong; Shenggang Liu; Zhuocheng Zhang; Tianyu Zhang; Yueying Wang
Terahertz Research Center, School of Electronic Science and Engineering, China

TDS s-SNOM, combining two powerful scientific research tools, has brought out promising capacity at nanoscale. In this work ,by analyzing four physical mechanisms in tip-cantilever-substrate model of TDS s-SNOM and simulating various parameters, we report on how tip-cantilever-substrate model affect near-field spectrum and local field density. Numerical simulation results are in good agreement with current experimental result.Further experiments are still in progress. This is of great significance to the development of TDS s-SNOM.

16:45 We-PM2-6-4
Modified AFM-tip For Infrared And THz Near Field Microscopy

Tahsin Akalin
Lille University, France

Near field microscopy is commonly achieved thanks to the exaltation of the field between a tip and the sample. The free space electromagnetic wave at infrared or THz frequencies is focused in this extremely small area compared to the wavelength. In many cases, the probe is a classical AFM-tip which was not made for this purpose. We present here an original approach in order to optimize the interaction between the impinging electromagnetic wave and the antenna-like probe. As a proof of concept we have modified with FIB (Focused Ion Beam) technique a commercial AFM-tip. The results in terms of resolution are very encouraging.

17:00-18:15 - Poster session We-Po3 - Room 8

Terahertz Distributed Amplifiers Based On Nanoscale Vacuum Phototubes

Jun Dai;
CunJun Ruan; Min Wang; Tian Miao; Yikun Ding
School of Electronic and Information Engineering, Beihang University, China

A high-speed nanoscale vacuum phototube (NVP) is theoretically studied. A small signal circuit model is proposed to characterize the high-frequency performance of an individual phototube. A traveling wave distributed amplifier (TWDA) based on high-frequency NVPs is demonstrated. And the transmission line model is introduced to analyze the voltage distribution and impedance of the TWDA. Our analysis provides a method for determining the optimum number of NVPs to realize high power TWDAs required in terahertz wireless systems and measurement instruments. I

20-vane Unstrapped 8-mm Magnetron Operation In Non-π-type Mode
Kostyantyn Ilyenko
IRE NAS of Ukraine, Ukraine

We report 20-vane-resonator unstrapped 8-mm (37.5 GHz) magnetron under development at IRE NAS of Ukraine. The device is supposed to operate in the "-1" spatial-harmonic. In order to provide better modes separation, a non-π-type mode is chosen as the operating one. Results of numerical modelling and experimental investigations of anode slow wave structure (anode block) for π/2-type mode are presented and discussed.

Design And Simulation Of A 0.2-THz Traveling-Wave Tube With Sheet Electron Beam Focused By Reversal Magnetic Filed

Nikita Ryskin1; Andrey Rozhnev1; Andrey Ploskih2; Vladimir Titov3; Anton Burtsev4; Igor Navrotsky4; Aleksei Danilushkin4
1Saratov Branch, Institute of Radio Engineering and Electronics RAS, Russian Federation; 2Saratov State University, Russian Federation; 3Saint Petersburg Electrotechnical University LETI, Russian Federation; 4RPE Almaz, Russian Federation

We study a 0.2-THz traveling-wave tube (TWT) with a grating slow-wave structure (SWS) and sheet electron beam focused by reversal magnetic field. Change in the direction of the guiding magnetic field causes change in the direction of beam curling and can suppress the diocotron instability, which is a main problem for sheet beam focusing. Electron gun with a converging sheet beam is designed and fabricated. Over 100 mA current was measured. The results of small-signal and large-signal TWT gain analysis are presented

Compact THz Continuous-Wave Clinotron Oscillators

Alexander Danik
1; Alexander Likhachev1; Sergey Ponomarenko1; Sergey Kishko1; Yurii Kovshov1; Viktor Zavertanniy1; Sergey Vlasenko2; Eduard Khutoryan1; Alexei Kuleshov1
1O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine; 2V. N. Karazin Kharkiv National University, Ukraine

Results of research and development of compact continuous wave clinotrons for THz applications are presented. The dependence of optimal phase shift per slow-wave structure period on the length of the system was investigated in 340 GHz continuous-wave (CW) clinotrons. Obtained experimental results show the maximal output power of 100 mW and electronic frequency tuning in the range from 320 GHz to 380 GHz that is in good agreement with the simulation results.

Injection Locking Of Resonant Tunneling Diode Oscillator With A Single-Frequency Terahertz Wave

Tomoki Hiraoka1; Takashi Arikawa1; Hiroshi Ito2; Koichiro Tanaka1
1Department of Physics, Graduate School of Science, Kyoto University, Japan; 2Center for Natural Sciences, Kitasato University, Japan

A resonant tunneling diode oscillator (RTD) has been successfully injection locked to a continuous terahertz (THz) wave. The locking range is about 80 MHz when RTD emission power and injected power are set to 10 µW and 4 µW, respectively. Locking range almost obeys a root-square injected-power dependence which is consistent with the Adler's theory.

Multicolor Terahertz Generation Via Spectrum-discretized Smith-Purcell Radiation

Weihao Liu; Yucheng Liu; Zijia Yu; Qika Jia; Yalin Lu
University of Science and Technology of China, China

The multicolor (multi-frequency) terahertz radiation is attractive for tremendous applications. Here we illustrate a set of schemes for multicolor terahertz generation, which uses a free-electron beam to excite an array of sub-groups of gradiently changed subwavelength units. Each unit has specific radiative resonant modes with the resonant frequency depending on structure parameters. Every sub-group has several resonant (radiative) frequencies. The multicolor radiation is obtained when the radiation from all sub-groups of the array constructively interfere via the special Smith-Purcell effect.

Experimental Advances In 220 GHz Sheet-Beam Traveling-Wave Tubes

Zhaoyun Duan1; Shengkun Jiang1; Guang Yang1; Tao Tang1; Zhanliang Wang1; Huarong Gong1; Yubin Gong1; Ye Tang2; Pan Pan2; Jun Cai2; Jinjun Feng2
1University of Electronic Science and Technology of China, China; 2Beijing Vacuum Electronics Research Institute, China

A 220 GHz sheet-beam Traveling-Wave tube (TWT) with output power 50 W was proposed. For the project, a sheet- beam electron gun with a circular cathode and a periodic cusped magnet-tunable quadrupolar magnet (PCM-TQM) focusing system are designed using the three-dimensional particle simulation software Opera 18R2. The experimental results show that the total current of the sheet-beam electron gun is consistent with the simulated beam current of ~135 mA. In addition, the transmission properties of the T-shape staggered double-grating slow wave structure (SWS) with input and output couplers were measured. The measured data show that there is a good passband within 15 GHz frequency range for the proposed TWT. In the future, the device performance will be reported.

Graphene And MoS2 Structures For THz Applications

Ayah Hijazi; Amine El Moutaouakil
UAE University, Department of Electrical Engineering, United Arab Emirates

In this work, we report on the plasmon frequency dependency of Graphene and MoS2 nanoribbon patterns on the angle between the plasmon wave vector and Graphene or MoS2 nanoribbons.

Research On 96GHz Sheet-beam EIO

Zhenhua Wu; Jielong Li; Chuanhong Xiao; Min Hu; Jie Qing; Bo Wang; Guanyi Zhang; Peipeng Wang
University of Electronic Science and Technology of China, China

Based on the 96 GHz sheet-beam EIO structure, this paper studies the cold cavity parameters and particle simulation of the structure. The results can provide a theoretical basis for the study of electric vacuum high frequency radiation sources.

Formation Of High-density Electron Flows By Electron-optical Systems With Multilayer Field Emitters
Gennadi Sominski; Vyacheslav Sezonov; Sergey Taradaev
Peter the Great St.Petersburg Polytechnic University (SPbPU), Russian Federation

This report presents the latest results of investigations of the operation of electron flow formation systems with multi-layer hafnium - platinum cathodes. The operation of systems for formation of sheet electron flows and systems for the formation of annular in cross section flows was studied. The investigated systems, including 20 pairs of hafnium and platinum layers, worked stably under technical vacuum conditions (10^-7 Torr) and provided extremely large emission current densities up to 300--400 A/cm^2, as well as full currents sufficient to ensure the operation of some type spectroscopic gyrotrons of terahertz and subterahertz range.

T-Channel JLFET THz Detector

Michal Zaborowski1; Daniel Tomaszewski1; Przemyslaw Zagrajek2; Jacek Marczewski1
1Institute of Electron Technology, Poland; 2Military University of Technology, Poland

A new type of JLFET based detector is described in the paper. This JLFET is equipped with additional electrode contacting side of the channel (giving T-like shape of the channel). The device offers higher photoresponse and better SNR and NEP than its standard counterpart. The most promising for application is -0.5 V .. 0 V gate voltage range, where 84 dB SNR is noted.

A Ka-band Backward-Wave Oscillator With Grating Slow-Wave Structure Developed By A Simplified Approach

Natsumi Ishiguro1; Yukihiro Soga1; Keisuke Iwabuchi1; Tatsuya Otake1; Masayuki Sato1; Yuya Ishikawa2; Seitaro Mitsudo2; Mitsuhiro Yoshida3
1Kanazawa University, Japan; 2University of Fukui, Japan; 3High Energy Accelerator Research Organization, Japan

We have devised a timesaving procedure for developing a Ka-band backward-wave oscillator (BWO) with a simple grating slow-wave structure (SWS). We developed a fast 1D-PIC code in radiation simulation to predict the output power for SWS of any design. In the experiment, we also developed an electron-beam transport system, which permits us to replace SWS without exposing the dispenser cathode to the air; thus, an efficient investigation for various kinds of SWSs has become possible. All the processes for developing the BWO, from a design of a SWS to the radiation experiment, were accomplished over several months. This time-saving development method is suitable for carrying out proof-of-principle experiments with various SWSs aiming at a high power THz BWO. Herein, we demonstrate the proposed approach by developing a 40 GHz BWO with a grating SWS.

Generation Of Trains Of Ultrashot Microwave Pulses By Two Coupled W-Band TWTs

Anton Ivanov
1; Maksim Nagornyuk1; Alexander Smirnov1; Naum Ginzburg2; Roman Rozental2; Mikhail Vilkov2
1SPE "Salut", Russian Federation; 2Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Russian Federation

Based on a time-domain model, we demonstrate that a periodic train of pulses can be generated in a system of two coupled W-band TWTs operating in regimes of amplification and saturable absorption, respectively. For saturable absorption the Kompfner dip regime implemented by a proper matching of the tube parameters. According to simulations with the parameters of an experimentally realized TWT, the peak power of generated pulses with a duration of 150 ps can achieve 100Ãf¢ââ?s‰â,¬Â°W.

Experimental And Numerical Study Of The 0.4-THz Second-Harmonic Gyrotron With A Complex-Cavity Resonator

Yoshinori Tatematsu1; Teruo Saito1; Masafumi Fukunari1; Yuusuke Yamaguchi1; Y Maeda1; T Ogura1; Maria Melnikova2; Andrey Rozhnev2; Nikita Ryskin2; Ilya Bandurkin3
1Research Center for Development of Far-Infrared Region, University of Fukui, Japan; 2Saratov Branch, Institute of Radio Engineering and Electronics RAS, Russian Federation; 3Institute of Applied Physics RAS, Russian Federation

Second-harmonic 0.4-THz gyrotron with complex-cavity resonator with TE8,3-TE8,5 mode conversion is studied. Cold-cavity electromagnetic parameters are simulated and start-oscillation current is calculated. The numerical results are compared with the experimental measurements.

W-band Pulsed TWT Family With Different Output Power

Anton Ivanov1; Maksim Nagornyuk1; Alexander Smirnov1; Roman Rozental2; Nikolai Peskov2
1SPE "Salut", SPE "Salut", Russian Federation; 2Institute of Applied Physics RAS, Russian Federation

Results of development and measurement of a series of pulsed TWTs at the W-band are presented. Simulations of the slow-wave and electron-optical systems have been carried out, the manufacturing technology has been developed, and TWTs based on the folded-waveguide slow-wave system have been realized. The measured output power varied from 5 to 50 W with a gain of up to 32 dB and an operation frequency band up to 6%.

Time Resolution And Power Dependence Of Transistor Based Terahertz Detectors

Przemyslaw Zagrajek1; Sergey Danilov2; Jacek Marczewski3; Michal Zaborowski3; Dariusz Obrebski3; Cezary Kolacinski3; Pawel Kopyt4; Dmitry But5; Wojciech Knap5; Sergey Ganichev6
1Military University of Technology, Poland; 2University of Regensburg, Germany; 3Institute of Electron Technology, Poland; 4Warsaw University of Technology, Poland; 5Institute of High Pressure Physics, Poland; 6University of Regensburg, Germany

We present a systematic study of time resolution and power dependence of the responsivity of three significantly different types of the state-of-the-art plasma based detectors. We analyze photoresponse of custom-made Si junctionless FETs (JLFETs), Si MOSFETs and GaAs-based high electron mobility transistors (HEMT) detectors, which represent structures that are very often employed in experiments dedicated to detection of sub-THz and THz radiation using FETs. All structures have been monolithically integrated with a log-periodic broad-band planar antenna. Time resolved photoresponse of room temperature detectors have been studied applying nanosecond pulses of monochromatic linearly polarized terahertz laser radiation with frequencies f ranging from 0.6 to 3.3 THz. Our measurements demonstrate that these detectors have nanoseconds response time and explore nonlinearity of detectors power dependence for different gate voltages applied to FET transistors

Application Of Clinotron Scheme For THz Traveling-Wave-Tubes

Alexander Danik; Alexander Likhachev; Sergey Ponomarenko; Sergey Kishko; Yurii Kovshov; Eduard Khutoryan; Alexei Kuleshov
O. Ya. Usikov Institute for Radiophysics and Electronics of NAS of Ukraine, Ukraine

Results of simulations of the 340 GHz TWT based on the clinotron operation scheme are presented. The advantage of applied clinotron scheme for THz TWT is demonstrated by the results of gain analysis, those were obtained according to non-linear non-stationary theory of the clinotron amplifier. The output power of simulated clinotron-TWT exceeds the power of ordinary TWT.

Results of simulations of the 340 GHz TWT based on the clinotron operation scheme are presented. The advantage of applied clinotron scheme for THz TWT is demonstrated by the results of gain analysis, those were obtained according to non-linear non-stationary theory of the clinotron amplifier. The output power of simulated clinotron-TWT exceeds the power of ordinary TWT.

Fmax=800GHz With 75 Nm Gate Length And Asymmetric Gate Recess For InGaAs/InAlAs PHEMT

Sylvain Bollaert; Mohammed Samnouni; Nicholas Wichmann; Xavier Wallart; Christophe Coinon; Sylvie Lepilliet
IEMN, University of Lille - CNRS, France

In this paper, we present a high maximum frequency of oscillation (fmax) and a current-gain cutoff frequency (fT) of 800 GHz and 260 GHz respectively with pseudomorphic high-electron mobility transistor (PHEMT), using a composite, InGaAs/InAs/InGaAs channel and an asymmetric gate recess. This result was achieved with long gate length LG = 75 nm. The noise performance has been explored until 110 GHz, and gives a minimum noise figure NFmin = 0.8 dB (1.8 dB) with associated gain Gass = 16 dB (11.6 dB) at 40 GHz (94 GHz). Moreover extending the drain recess length to 225 nm and reducing the gate to source distance by 200 nm allows a fmax = 1.2 THz.

Coherent Terahertz Radiation From Homogeneous Intrinsic Josephson Junction Stacks Of Cuprate High-Temperature Superconductors

Manabu Tsujimoto; Genki Kuwano; Yota Kaneko; Takayuki Imai; Yukino Ono; Shungo Nakagawa; Shinji Kusunose; Takanari Kashiwagi; Hidetoshi Minami; Kazuo Kadowaki
University of Tsukuba, Japan

A stack of intrinsic Josephson junctions of high-temperature superconductors is emerging as compact sources of coherent THz radiation. We present an effective engineering technique for accurately controlling sidewall angles of the mesa structure made of single crystalline Bi2Sr2CaCu2O8+δ. We investigate the effect of homogeneity of stacked junctions on synchronization using two mesas with varying sidewall angels. The radiation intensity can be suppressed significantly when the sidewall is tilted more than ~10%. This finding allows us to construct higher power sources based on superconductors that are able to fill the technological gap in the sub-THz regime.

High Performance Surface Plasmon Polaritons From Mediated Coupling Excitation

Sen Gong; Wei Wang; Tao Zhao; Min Hu; Diwei Liu; Zhenhua Wu; Renbin Zhong; Shenggang Liu
University of Electronic Science and Technology of China, China

Graphene surface plasmon polartions (GSPs) opens a promising way for terahertz sources. However, there are still many challenges for the current GSPs electric excitation methods. Here, high performance GSPs from the mediated coupling is presented, which are excited by the coupling between the GSPs in graphene based hyperbolic medium (GHM) and spoof surface plasmons (SSPs) in a designed grating. Compared with current methods, there are many advantages, as low propagation loss, strong coherence, wide tuning bandwidth and large power density. Therefore, this work is of great significance of terahertz radiation sources.

On The Effect Of Quantum Capacitance In Graphene FET THz Detectors

Mehdi Hasan; Berardi Sensale-Rodriguez
University of Utah, United States

We analyze the impact of quantum capacitance on the response of graphene-based field effect transistors (FETs) operating as THz detectors. Resulting from its atomically thin body and its particular band structure, the quantum capacitance in graphene has different behavior than that in bulk-semiconductor two-dimensional electron gases. Furthermore, we analyze and identify non-homogeneities and impurities, which in practice lead to a finite minimum effective charge density as well as to a finite minimum conductivity in graphene, as an effect that can degrade the predicted theoretical performance of graphene-based THz devices.

Control Of Mesa Sidewalls For Coherent Terahertz Radiation From Intrinsic Josephson Junctions Of High-Tc Superconductors

Genki Kuwano; Yota Kaneko; Takayuki Imai; Yukino Ono; Shungo Nakagawa; Shinji Kusunose; Takanari Kashiwagi; Hidetoshi Minami; Kazuo Kadowaki; Manabu Tsujimoto
University of Tsukuba, Japan

Compact and solid-state CW terahertz sources based on stacks of intrinsic Josephson junctions of high-Tc superconductors are interested in both scientific and industrial fields. In this study, we focus on the effect of the mesa sidewalls associated with variation in characteristics of the stacked junctions. We implement an effective laser lithography to pattern two neighboring mesas with varying sidewall angles on the identical superconducting crystal base. The intense radiation is observed only from the mesas with rather vertical sidewalls, suggesting that the distribution uniformity is a key ingredient to promote the spontaneous synchronization among thousands of intrinsic junctions.

A Graphene Self-Switching Diode Bridge Rectifier

Joseph Brownless; Jiawei Zhang; Aimin Song
University of Manchester, United Kingdom

Here we present theory and measurements for a bridge rectifier formed from arrays of graphene self-switching diodes (GSSDs). Graphene's extremely high carrier mobility allows GSSDs to work at THz frequencies, with the bridge rectifier structure allowing for full wave rectification of an AC signal. We derive an equation for the voltage output of a GSSD bridge rectifier, predicting a quadratic dependence on input current. This relationship is confirmed using AC and DC measurements. The fabricated rectifier has a high room temperature intrinsic responsivity of 3,230 V/W at low frequency and a low noise equivalent power of 7.0 pW/Hz^1/2.


Stokes-parameter Analysis Of Circular Polarized Terahertz Waves From Superconducting Josephson Plasma Emitter

Keiichiro Maeda; Shuma Fujita; Asem Elarabi; Manabu Tsujimoto; Itsuhiro Kakeya
Kyoto University, Japan

We have been studying terahertz sources which consists of intrinsic Josephson junctions of high-Tc superconductors. In this paper, we identify the helicity of terahertz waves emitted from the device of high-Tc superconductors by using a quarter-wave-plate (QWP) of terahertz band. We can observe the right-handed circular polarization from the terahertz source. Moreover, the obtained Stokes parameters are consistent with data of axial ratio measurements without the QWP. We plan to identify the helicity about other positions of current injection.

Negative Differential Resistance In ZnO-based Resonant Tunneling Diodes

Vadim Sirkeli
1; Sergiu Vatavu2; Oktay Yilmazoglu1; Sascha Preu1; Hans Hartnagel1
1Technische Universitat Darmstadt, Germany; 2Moldova State University, Republic of Moldova

We present the results of a simulation study of resonant tunneling transport of non-polar m-plane ZnO/ZnMgO quantum structures with double and triple quantum barriers. It is found that in current density-voltage characteristics of such devices a region is present with negative differential resistance and this feature can be used for the generation of terahertz waves. The best performance at room temperature with output power of 912 µW @ 1 THz is derived for the non-polar m-plane ZnO/ZnMgO structures with triple quantum barriers and optimized design.

Terahertz Radiation From The High-Tc Superconductor Intrinsic Josephson Junctions Coupled To An External Resonator

Yukino Ono; Hidetoshi Minami; Genki Kuwano; Shinji Kusunose; Takayuki Imai; Yota Kaneko; Shungo Nakagawa; Takanari Kashiwagi; Manabu Tsujimoto; Kazuo Kadowaki
University of Tsukuba, Japan

Continuous and coherent terahertz radiation is emitted from mesa-shaped devices made of the intrinsic Josephson junctions (IJJs) in high-Tc superconductor Bi2Sr2CaCu2O8+ÃfÆ'Ã?â?TÃfâ?¦Ã,½ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,´. In this study, we have for the first time succeeded in separating the functions of resonator and antenna from the IJJs mesa, by miniaturizing the mesa to about 1/70 of the conventional ones and by coupling it to an external patch resonator. We have observed radiation at designed resonant frequencies and directivity of the patch resonator/antenna. The radiation intensity per mesa area is a few times bigger than typical ones of the conventional mesa devices. This result provides us with an effective way to improve the radiation characteristics and extend the radiation frequency.

A Scalable Photomixing Array For Increased Emitted Power

Alvaro Pascual-Gracia1; Mushin Ali2; Luis-Enrique García-Muñoz2; Guillermo Carpintero2; David González-Ovejero1; Ronan Sauleau1; Frédéric Van Dijk3
1IETR, France; 2UC3M, Spain; 3III-V Labs, France

The goal of this work is to increase the emitted power at E band using a photomixing antenna array. The antenna architecture has been selected to yield a scalable design, high efficiency, and bandwidth (> 10%). A first prototype has been tested in a communications link with one active photodiode at a data rate of 2.15 Gb/s and 25 cm distance.

Unit-cell Design For Antenna Arrays Efficiently Matched To Uni-travelling-carrier Photodiodes

Alvaro Pascual-Gracia1; David González-Ovejero1; Ronan Sauleau1; Luis-Enrique García-Muñoz2
1IETR, France; 2UC3M, Spain

We present an antenna array conceived to obtain efficient matching to integrated sources or loads with low input resistance using a backing grid. From an infinite array approach, we derive closed-form expressions for the different elements in the equivalent network representation. This analytic approach enables the preliminary design of arrays with improved matching efficiency for optimum power transmission/reception. A solution matched to a uni-travelling-carrier photodiode is presented with a maximum 3 dB power improvement compared to a 72 ? antenna, featuring 50 % bandwidth.

90 GHz Branch-line Coupler On GaN-on-Low Resistivity Silicon For MMIC Technology

Bhavana Benakaprasad1; Abdalla Eblabla1; Xu Li2; Khaled Elgaid1
1Cardiff University, United Kingdom; 2Glasgow University, Nanotechnology, United Kingdom

We demonstrate a quadrature branch-line coupler operating at 90 GHz on GaN-on-low resistivity silicon substrates (ρ < 40 â"¦.cm). To reduce the losses offered by the low-resistivity silicon at 90 GHz, a shielding technique is used where the silicon substrate is covered by ground plane (Al metal). SiO2 dielectric of thickness 10 µm is used as a spacer between the top metal and ground plane to further improve the performance of the coupler. Measured results showed return loss and isolation as low as -25 dB and -16 dB respectively, and coupling loss of -4 ± 0.5 dB from 81 GHz to 101 GHz. The output amplitude imbalance achieved was less than 5 dB. The coupler validates the shielding MMIC technology on GaN-on-low resistivity silicon substrate.

The Effect Of Phosphor Coating On THz/mm Wave-Plasma Interaction In Glow Discharge Detector

Cemre Kusoglu Sarikaya; Demiral Akbar; Hakan Altan
Middle East Technical University, Department of Physics, Turkey

Glow discharge detectors (GDDs) attract attention because they have advantageous features compared to commercial detectors currently used for detecting THz and mm waves. Studies in the literature show that N523-coded GDD which has a phosphorous coating exhibits the best performance. However, to the best of our knowledge, no study has been carried out yet to demonstrate the effect of phosphorus coating on the detection mechanism. Therefore, in this study, it is aimed to understand this effect by simulating the plasma consisting of Ne-Xe mixture in N523 coded GDD with the parallel 1d3v Particle in Cell/Monte Carlo Collision (PIC/MCC) code.

Z-Shaped Dual Band Circular Polarized Microstrip Antenna For THz Communication

Shahid Ullah;
CunJun Ruan; Tanveer Ul Haq
chool of Electronic and Information Engineering, Beihang University, China

In this paper a simple z-shaped dual band circular polarized (CP) terahertz (THz) monopole antenna is designed for short range communication applications. Circular polarization is obtained by rotating the z-shape radiating element by 450 around the horizontal plane with microstrip line. The antenna is operating at dual band with bandwidth of 50 GHz (0.19-0.24 THz) and 340 GHz (0.27-0.61THz). It has a left hand circular polarized (LHCP) antenna having below 3dB axial ratio with bandwidth of 110 GHz (0.38-0.49 THz) and 15 GHz (0.575-0.59 THz). The total dimension of the antenna is 850ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'Ã,¢Ãf¢ââ,¬Å¡Ã,¬"770ÃfÆ'Ã?â?TÃfâ? Ã¢â,¬â"¢ÃfÆ'Ã,¢Ãf¢ââ,¬Å¡Ã,¬"197 ÃfÆ'Ã?â?TÃfâ?¦Ã,½ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,¼m3

A Schottky Diode Multiplier Chain Based On Three-dimensional Stacking Integration At 410GHz To 510GHz

Jun Jiang1; Chen Peng1; He Yue1; Li Li1; Tian Yaoling1; Hao Hailong2
1Microsystem and Terahertz Research Center (MTRC), CAEP, China; 2IEE, CAEP, China

The research introduced the integration technology of three-Dimensional stacked terahertz transmitter link based on schottky diode multiplier at 410GHz to 510GHz. In the multiplier chain, there are five stages: the E-band multiplier, E band drive amplifier, D-band doubler and antenna. Firstly, the five different parts have been designed separately. Secondly, the different stage has been designed onto different layers, and the transmission direction has been changed to vertical direction from horizontal direction. Finally, the 3D stacked terahertz transmitter has been finished, and it is smaller than the separate modules with the similarly results. The final size changed from 110mm to 13mm, and the performance is similar to the chain based on discrete modulesï¼Å'which is better than 50uW.

A 410-510GHz Room Temperature Local Oscillation Source For SIS Mixers

Peng Chen1; Li Li1; Kun Huang1; Shengcai Shi2; Kun Zhang2
1Microsystem and Terahertz Research Center, China Academy of Engineering Physics, China; 2Purple Mountain Observatory, China

A 410-510GHz local oscillation source for SIS mixers has been designed, fabricated, and tested. The source is a Ã- 24 frequency multiplier working at room temperature. It converts the input low band microwave signals to submillimeter signals. It is comprised of an E band quadrupler, a bandpass filter, a power amplifier, a D band doubler and a final trippler. Both of the D band doubler and the final trippler use plannar Schottky diodes and quartz based circuits to realize frequency multiplication. Over the 410-510GHz band, the output power of the source is above 50uW, and the maximum is 122uW in 461.8GHz. A horn antenna is connected with the source to radiate the power to SIS mixers which are used for submillimeter radio telescope in Purple Mountain Observatory in China.

Dielectric Rod Antenna Array For Photonic-Based Sub-Terahertz Beamforming

Serguei Smirnov1; Alvaro Morales2; Chigo Okonkwo2; Idelfonso Tafur Monroy2; Dmitri V. Lioubtchenko1; Joachim Oberhammer1
1KTH Royal Institute of Technology, Sweden; 2Eindhoven University of Technology, Netherlands

This work presents a dielectric rod antenna array designed for a photonic-enabled beamforming system at sub-terahertz frequencies. The photonic chip generates an optical time delay, providing the beam-steering capability. The antenna array is fabricated from high-resistivity silicon by micro-machining. Simulation results demonstrate a directivity of 14.7 dBi and a beam steering range of 56 degrees at 85 GHz. The system is intended as a sub-THz transmitter for broadband wireless communications.

Graphene Microfabrication For Developing Mm-wave And THz Devices

Andrew Squires; Michael Seo; Simon Lam; Xiang Gao; Ting Zhang; Zhaojun Han; Jia Du
CSIRO, Australia

This paper investigates the microfabrication process of graphene in developing high frequency, particularly millimeter-wave and terahertz, electronic devices. We consider graphene production, transfer, fabrication and electrical characterization. Preliminary results reveal key insights including the benefit of polymer removal in transferring graphene to substrates as well as identifying Ar ion beam etching as being effective in patterning graphene thin films. This work lays a solid foundation in developing a holistic and reliable method to pattern graphene for use in high frequency electronics components.

Design, Fabrication And Measurement A Promising Photonic Crystal-like Structure Inside A Rectangular Waveguide

Andrey Starodubov; Artem Badarin; Semen Kurkin; Anton Pavlov; Victor Galushka; Yurii Kalinin; Alexey Koronovskii
Saratov State University, Russian Federation

Experimental and numerical studies of an electrodynamic structure assembled according to photonic crystals' principles placed inside the X-band rectangular waveguide are considered. Such structures are promising for microwave electronics (vircators, FELs, and etc.). Efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes is one the most valuable features of dispersion characteristics of photonic crystal-like structures. The proposed electrodynamic structure is a 2D array of thin metal pins. Transmission and reflection characteristics of the proposed structure were measured experimentally and evaluated numerically in K, Ka and Q bands. The experimental results are in good agreement with the numerical ones.

Via-less Microstrip To Rectangular Waveguide Transition On InP

Bilal Hussain1; Giovanni Serafino2; Paolo Ghelfi2; Antonella Bogoni3; Andreas Stöhr4
1Suola Superiore Sant'Anna, Italy; 2CNIT, Italy; 3Scoula Superiore Sant' Anna, Italy; 4University of Duisburg Essen, Department of Optoelectronics, Germany

Indium-Phosphide (InP) is one of the most common materials used for realizing active devices working in the millimeter frequency range. The isotropic etching profile of InP substrates limits the realization of passive devices, thus requiring an expensive and lossy hybrid platform. This paper presents a via-less, cost-effective and efficient solution for InP substrate. By using the proposed planar solution, it is demonstrated that rectangular waveguides can be realized on InP by fabricating a bed of nail structure which acts as a reflecting boundary for an impinging millimeter wave. As a proof of concept, a transition from microstrip to rectangular waveguide structure is realized within H-band (220-320 GHz) with a return loss of -18dB over a bandwidth of 30 GHz.

Schottky Diode Based 220GHz Receivers Operating At Room-Temperature For Passive Security Scanning

Haifan Hu; Xuming Ma
Department of Engineering Physics/ Tsinghua University, China

The designed and fabricated of a 200~240GHz receiver for use with THz radiometers is presented. The receiver is based on a sub-harmonic mixer developed by GaAs Schottky diode, its conversion losses of single sideband (SSB) are 7~12 dB, and it requires 5mW local oscillator (LO) power, which is driven by a 110GHz tripler with about 4% efficiency over the band 105~118GHz, and the maximum efficiency of 5.5% output power has been measured at 108.6GHz.

Silicon Based Diode Noise Source Scaling For Noise Measurement Up To 325 GHz

Haitham Ghanem1; Joao Carlos Azevedo Gonçalves2; Sylvie Lépilliet1; Daniel Gloria2; Christophe Gaquiere1; François Danneville1; Guillaume Ducournau1
1IEMN, CNRS UMR 8520, France; 2STMicroelectronics, France

In this article, we investigate the use of silicon-based diode for millimeter-wave noise generation. A test bench setup was characterized to perform broadband noise measurements up to 325 GHz. A noise receiver is assembled and its Noise Figure (NF) was extracted using cryogenic Hot/Cold measurements. A unitravelling carrier photodiode (UTC-PD) is used as a noise source and the Excess Noise Ratio (ENR) is extracted using the Y-method, and used as a reference for 300 GHz noise generation. The ENR value of the UTC-PD is to be compared to that of a silicon based integrated diode noise source, which will be tested to perform noise measurements up to 325 GHz.

Application Of Sub-THz Circular Dichroism Quasi-Optics To Probe The Conformality Of Solvated Protein

Jhih-Hong Cheng1; Robert Jones1; Oleksandr Sushko2; Bin Yang3; Yumiko Tashiro1; Robert Donnan1
1Queen Mary University of London, United Kingdom; 2Igor Sikorsky Kyiv Polytechnic Institute, Ukraine; 3University of Chester, United Kingdom

A sub-terahertz (sub-THz) Circular Dichroism (CD) quasi-optical (QO) system has shown utility in acquiring electromagnetic absorption signatures of solvated protein samples over H-band frequencies (220 -- 325 GHz). We report the sub-THz CD signature of Myoglobin in particular. Spectra are reproducible within experimental error

Research And Design Of W-Band Waveguide Mode Generator

Lanyue Qi; Xinjian Niu; Jinhao Li; Jianwei Liu
University of Electronic Science and Technology of China, China

In this paper, the research of W-band TE62 coaxial mode generator is studied in detail, and the purity of the mode is improved by selecting a complex coaxial cavity. In order to improve the ability to suppress the unwanted mode, the optimized three-stage smooth coaxial cavity has been used. based on the method of the surface impedance matching theory, the resonant cavity was designed and optimized using the code writing by MATLAB program. Finally, the commercial electromagnetic simulation software is used for verification. The simulation result shows that the purity of the mode exciter is 96.80% when the resonant frequency is 94.12 GHz.

A 240 GHz Receiver With 6 Gb/s Data Rate Based On Plasma Wave Detection In SiGe Technology

Kefei Wu1; Guillaume Ducournau2; Mona Hella1
1Rensselaer Polytechnic Institute, United States; 2University of Lille, France

This paper presents a fully integrated 240 GHz plasma-wave Field Effect Transistor (FET) direct-detector receiver, implemented in 130 nm Silicon Germanium (SiGe) technology(fT =fmax = 210/250 GHz). The receiver chain is formed of an on-chip patch antenna, plasma-wave detector, and a broadband amplifier. The low modulation frequency characterization shows a responsivity of 15 V/W at 240 GHz, with a drain bias current of 2 µA. The responsivity is higher than 10 V/W from 225 GHz to 250 GHz. When measured with modulated signals at a carrier frequency of 240 GHz, the detected signal shows a clear eye diagram at a data rate up to 6 Gb/s with a bit error rate less than 10E-5.

Tunable Notch Filter For Measurements Of Rogue Waves In Gyrotrons

Anton Gashturi1; Mikhail Goykhman1; Alexander Gromov1; Sergey Filchenkov1; Alexey Palitsin1; Alexander Panin2; Yuri Rodin2; Roman Rozental2; Nikolai Peskov1
1Institute of Applied Physics RAS, Russian Federation; 2Institute of Physics of Microstructures RAS, Russian Federation

A novel design of notch filter was proposed and tested. Waveguide filter consists of a prismatic resonator coupled to waveguide by a slot and a frequency tuning plunger. We intend to apply this filter for measuring the output radiation of Ka-band gyrotron operating in regime of rogue wave generation and for microwave plasma diagnostics. X-band prototype of the filter was manufactured and its characteristics were measured.

A 3D Printed Waffle Type Waveguide For Millimeter Wave Application

Kenji Itagaki1; Motonori Doi2; Toru Hara3; Sang-Seok Lee3
1Tottori Univeristy, Japan; 2Osaka Electro-Communication University, Japan; 3Tottori University, Japan

In this paper, we report a 3D printed waffle type waveguide for millimeter wave application. The waveguide consists of a waveguide part and two filter parts for electromagnetic wave transmission and attenuation, respectively. We fabricated the waveguide using a selective laser sintering metallic 3D printing technique, and achieved smaller reflection loss than -20 dB and low insertion loss from 22.3 GHz to 34.0 GHz.

Impedance Matching Networks Designed By Evolutionary Algorithms

Vanessa Fenlon; James McCubbin; Claudio Balocco
Durham University, Engineering Department, United Kingdom

A key challenge to extend the operation of electronics nanodevices to mm-wave and THz frequencies is the large impedance mismatch among all components. Here we propose a methodology based on a genetic algorithm coupled to a 3D electromagnetic simulator for designing compact matching networks suitable for operation up to THz frequencies. Both narrow and broad band networks can be realized with the same approach, simply by changing to a suitable fitness function. Structures showing a theoretical voltage standing-wave ratio below 1.03 were obtained for a narrow band circuit centered at 1 THz and below 1.29 in the range 0.95-1.15 THz with a load impedance of 1 kΩ.

Millimeter-wave-triggering Of Insulator-to-metal Transition In Vanadium Dioxide

Fatemeh Qaderi1; Andrei Muller1; Anna Krammer1; Miroslav Veljovic1; Zoltan Ollmann2; Mozhgan Hayati2; Anja Skrivervik1; Andreas Schueler1; Thomas Feurer2; Adrian Ionescu1
1Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland; 2University of Bern, University of Bern, Hochschulstrasse 6, Bern, Switzerland
We establish insulator-to-metal transition (IMT) in Vanadium dioxide (VO2) by millimeter-wave (mm-wave) actuation, using two coupled dipole antennas: a simple one as a continuous mm-wave-source and the other one with an embedded VO2 part as an absorber. We measured |S12| by a vector network analyzer (VNA), to show how the induced mm-wave power in insulating biased VO2 causes IMT. The bias voltage is set to enhance the sensitivity in VO2. The VO2 embedded antenna shows sensitivity to the mm-wave power down to 3.2 μW. The experiment proves the detection concept also for terahertz frequencies.

A 0.13 THz Amplifier Integrated With A Frequency Doubler For A 0.26 THz 0 DBm Output Power
Hao Gao1; Jixin Chen2; Wei Hong2; Peter Baltus1
1Eindhoven University of Technology, Netherlands; 2Southeast University, China

This contribution presents a 0.26 THz power unit in a 0.13 Ã,µm SiGe BiCMOS technology. This submillimeter-wave frequency power unit is composed of a 2-stage 0.13 THz amplifier integrated together with a 1-stage frequency doubler. In an active submillimeter-wave frequency array, the size of the power unit is critical. In this work, a compact power unit is achieved through on-chip broadside transformers. With this compact solution, the area of the core part of this power unit is 110*900Ã,µm2 and the output power at 0.26 THz is 0 dBm.

Comparison Of Fourth-harmonic And Combined Doubler/Subharmonic Mixer With Integrated MMIC Based Local Oscillator

Jose M. Pérez-Escudero; Carlos Quemada; Iñigo Ederra; Ramón Gonzalo
Public University of Navarra, Spain

In this paper a comparison between a fourth harmonic mixer and a combined doubler/subharmonic mixer based on Schottky diodes working at 300 GHz with MMIC Local Oscillator (LO) integrated in single enclosing is presented. Both configurations allow reducing the LO requirements, since a lower LO frequency is used. In addition, the integration of the MMIC Local Oscillator with the mixer in the same single metallic block allows avoiding flange connections. This way, misalignment errors are also prevented. In addition, the compactness of this solution is also remarkable, leading to a significant weight reduction.

Long-Distance Coherent Signal Transmission And Reception Of Optically-Connected 96 GHz Millimeter-Wave Radar System For Runway Foreign Object Debris Detection

Shunichi Futatsumori; Kazuyuki Morioka; Akiko Kohmura; Naruto Yonemoto
Electronic Navigation Research Institute, Japan

To detect the small foreign object debris (FOD) on the airport runway, the FOD detection system based on the optically-connected 96 GHz distributed-type millimeter-wave radar have been developed. In this paper, long-distance coherent signal transmission and reception for Radio-over-Fiber (RoF) based radar system are discussed. The coherent signal network based on optical wavelength division multiplexers. In addition, the radar transmission signal and the receiving signal are transferred by the millimeter-wave RoF and 10 gigabit Ethernet, respectively.

Performance Characterization Method Of Broadband Terahertz Video Cameras

Vishal Jagtap; Robin Zatta; Janusz Grzyb; Ullrich Pfeiffer
Institute for High Frequency & Communication Technology, Germany

Integrated THz systems comprising index matched optical media introduce discontinuities in the propagation path leading to an etaloning effect. The etaloning hinders the absolute accuracy of a measuring instrument thereby limiting its applicability. A methodology using computational notch filtering is implemented here to extract the true performance of a measuring instrument. Specifically, the responsivity and NEP of the portable room temperature 1k-pixel terahertz CMOS camera have been investigated using a continuously tunable broadband spectrally pure terahertz photomixer source. Applying methodology revealed a peak responsivity of 20 MV/W at 822 GHz with a 6-dB bandwidth of 265 GHz and a minimum integrated NEP of 2.9 nW with 1024 frames averaging at 30fps.

Laser-Driven Semiconductor Switch As A Diagnostic Method In Terahertz Band

Maxim Kulygin
Institute of Applied Physics, Russian Federation

A conception of using a laser-driven resonator cavity switch as a diagnostic method for semiconductors in terahertz frequency band is presented. The resonant behavior allows one to achieve good accuracy in measuring the semiconductor's permittivity and loss tangent. The method features extremely low amount of semiconductor needed for the analysis in comparison with known methods.

THz Conductivity In Metal Organic Frameworks (MOF)

Jens Neu; Brian Pattengale; Jacob A. Spies; Sarah Ostresh; Uriel Tayvah; Chalres A. Schmuttenmaer
Yale University, United States

Metal organic frameworks (MOFs) are an emerging class of materials. These materials exhibit a large degree of porosity resulting in a low density. These are promising attributes for the fabrication of low-weight and wearable electronics. In this submission, an electrically conductive MOF is investigated. We present temperature-resolved THz-TDS measurements, OPTP, and TRTS measurements. We detected several low energy vibrational excitations in the TDS traces, as well as photoconductivity in the OPTP and TRTS. These measurements provide a pathway to explain the underlying processes of conductivity in this material system.

Broadband Characterization Of Glass And Polymer Materials Using THz-TDS

MD SAIFUL ISLAM1; Jakeya Sultana1; Cristiano. M. B Cordeiro2; A. L. S Cruz3; Alex Dinovitser4; Brian W.-H Ng4; Derek Abbott4
1The University of Adelaide, Australia; 2The University of Adelaide, IPAS, Australia; 3Braz Cubas University, Brazil; 4The University of Adelaide, EEE, Australia

The optical properties of polymers and glasses of interests are experimentally characterized using terahertz time domain spectroscopy (THz-TDS). Transmission spectroscopy are used to extract the dielectric properties of Topas (cyclic olefin co-polymer), Zeonex (Cyclo-olefin polymer), Polytetrafluoroethylene (Teflon), high-density polyethylene (HDPE), Polymethyl methacrylate (PMMA), Silica, BK7, Duran and UV-Resin in the terahertz band.

Optical Properties Of Polymers In THz Regime And Their Discrimination

Muhammad Mumtaz1; M. Ahsan Mahmood2; Sabih D Khan3; M. Aslam Zia3; Mushtaq Ahmed3; Izhar Ahmad3
1National Institute of Lasers & Optronics, Pakistan; 2Pakistan Institute of Engineering and Applied Sciences, Pakistan; 3National Institute of Lasers and Optronics (NILOP), Pakistan

A scheme for the discrimination of different types of polymers using Terahertz time domain spectroscopy (THz-TDS) along-with chemometrics has been presented. Moreover, this work has been extended for the measurement of temperature-dependent optical properties of these polymers and extraction of coefficients of Sellmeier Equation.

Multifunctional Graphitic Thin Films For Terahertz Range

Tommi Kaplas1; Ignas Nevinskas1; Andrzej Urbanowicz1; Petr Obraztsov2; Alesia Paddubskaja3; Marian Baah4; Irmantas Kasalynas1
1Center for Physical Sciences and Technology, Lithuania; 2A. M. Prokhorov General Physics Institute, Russian Federation; 3Institute for Nuclear Problems of Belarusian State University, Belarus; 4University of Eastern Finland, Finland

Tunability of optical properties of the thin graphitic films (GRFs) makes them versatile for ultra-wide spectral range optics, including terahertz (THz) and microwave optics. Here we report THz properties of a GRF material synthetized directly on a dielectric substrate. Our GRF samples demonstrated about 50 % absorption at VIS-IR and ~15 % absorption at THz (0.5-1.5 THz range). Transmittance of THz waves through the sample could be modulated by absorption of free-carriers induced in the GRF by applied voltage and photo-excitation. Therefore, the reported GRF material shows great potential for electrical/optical modulation of THz and microwave range photonics.

Absorption Properties Of 3D-printing MWCNT Composites At The THz Frequency Range

Alexander Badin; Kseniya Simonova; Grigorii Kuleshov; Valentin Suslyaev; Grigorii Dunaevskii; Kirill Dorozhkin; Diana Pidotova; Dmitriy Bodazhkov
National Research Tomsk State University, Russian Federation

Currently, the main method of ensuring electromagnetic compatibility in terms of resistance to the effects of an electromagnetic field, as well as compliance with the requirements for the level of radiated interference, is electromagnetic shielding. Special structures and various materials are used for shielding electromagnetic fields. Among these materials, multi-walled carbon nanotubes (MWCNTs) occupy a special place. MWCNTs are distinguished by their ease, and they are also electrically conductive. In combination with modern additive technologies, such as 3D printing, it is possible to create surfaces of complex geometry with the absorbing properties of electromagnetic radiation in a wide frequency range, including THz. Thus, it is of interest to research the absorbing properties of a material based on dielectric matrix of acrylonitrile-butadiene styrene (ABS) and MWCNTs obtained by additive technology. In paper results of research of absorption properties of 3D-printing MWCNT composites at the 115-258 GHz frequency range are presented.

Insulator-metal Transition In PrYCaCoO3 Thin Films Studied By Terahertz and Infrared Spectroscopies

Christelle Kadlec1; Karel Knizek1; Jiri Hejtmanek1; Veronika Goian1; Josef Bursik2; Miroslav Soroka2; Hynek Nemec1
1Institute of Physics CAS v.v.i., Czech Republic; 2Institute of Inorganic Chemistry CAS v.v.i., Czech Republic

Charge transport in PrYCaCoO3 thin films was studied experimentally by terahertz (THz) and infrared spectroscopies and by dc conductivity measurements. The metal-insulator transition is clearly visible in THz conductivity, whereas the observed weak temperature dependence of dc conductivity is limited by inter- grain charge transport.

Including The Effects Of Covering Layers In The Determination Of Graphene
Conductivity From THz-TDS Measurements
Daniel Stock; Christoph Suessmeier; Peter Haring Bolívar
University of Siegen - High Frequency and Quantum Electronics, Germany

We investigate the effects of covering layers on the determination of graphene conductivity from THz-TDS measurements. Especially the errors arising from the common approach to neglect those layers in the determination process are addressed. To counteract those errors an expanded determination method, based on the classical thin-film approach is introduced.

THz Properties Of Fe And Ti Oxides Nanoparticles Obtained By Pulsed Laser Ablation

Dmitry M. Ezhov1; Nazar A. Nikolaev2; Alexander A. Mamrashev2; Valery A. Svetlichnyi1; Victor N. Cherepanov1
1Tomsk State University, Russian Federation; 2Institute of Automation and Electrometry SB RAS, Russian Federation

We present Dielectric properties of Fe and Ti oxides nanoparticles (NPs) measured by THz-TDS. The NPs were obtained via ns pulsed laser ablation (PLA) of the metals in air and water and were annealed at different temperatures. We report here the dependence of absorption spectra on NPs structure: from magnetite to hematite for Fe, and from anatase to rutile for Ti. The prospects for their use as materials for the THz photonics are discussed.

Terahertz Proton Motions In Proton-Conducting Electrolyte Of Solid Oxide Fuel Cell
Hikaru Takehara1; Tomohide Morimoto1; Masaya Nagai1; Masaaki Ashida1; Yuji Okuyama2; Yukimune Kani3
1Osaka University, Japan; 2University of Miyazaki, Japan; 3Panasonic Corporation, Japan

proton conductor has attracted us as a solid electrolyte of the next generation solid oxide fuel cell with high energy conversion efficiency. Doped BaZrO3 perovskite is one of the most promising solid electrolytes with high proton conductivity. Long-range kinetics of protons in doped BaZrO3 have been investigated through low-frequency impedance measurement, diffusion coefficient measurement, NMR measurement. In this report, we demonstrate that THz conductivity measurement is a powerful tool for investigating the picosecond proton dynamics in proton-conducting electrolyte of solid oxide fuel cell. We measure the THz conductivity in the protonconducting solid electrolyte, BaZr0.8Y0.2O3, with THz time-domain spectroscopy at high temperature. Observed sub-THz conductivity reflects the breaking and reforming hydrogen bonding, which is related to the proton hopping between neighboring oxygen atoms. Our results will open a new application of THz spectroscopy for direct characterization of the proton dynamics in solid electrolyte of fuel cell.

Optimization Of Terahertz Wave Generation From Nonlinear Optical Crystal Using Amorphous Fluoropolymer Coating

Keisuke Matsumura1; Yudai Ikegami1; Peibin Wang1; Hirohisa Uchida1; Chisa Koyama2; Takeshi Takagi2; Kei Takeya1; Kodo Kawase1
1Nagoya University, Japan; 2ARKRAY Inc., Japan

The amorphous fluoropolymer CytopTM is a coating material for organic nonlinear optical crystals. As a coating material, it acts as both an antireflection coating and a protective layer for the crystal itself in advanced terahertz (THz) wave generation applications. In this study, we report on the optical parameter in THz frequency over a wide temperature ranges, and the optimization of THz wave generation from a Cytop-coated nonlinear optical crystal.

Mid-IR S-SNOM Imaging Of Photo-induced Refractive Index Variation In Chalcogenide Glass

Louis Thomas1; Sophie Eliet1; Julie Carcreff2; Jean-François Lampin1; Eugène Bychkov3; David Le Coq2; Pascal Masselin3
1IEMN, France; 2Institut des Sciences Chimiques de Rennes, France; 3Laboratoire de Physico-Chimie de l'Atmosphère, France

We report the mid-IR s-SNOM surface characterization of a chalcogenide glass photo-inscribed by ultrashort laser pulses. Imaging allows to access to the morphology and the optical properties of the material at nanoscale, unravelling topographical and optical contrasts resulting from the laser inscription process.

Observation Of Strong Yellow Emission For High-conductivity ZnO Excited By Sub-terahertz Gyrotron Beam

Makoto Nakajima1; Kosaku Kato1; Hongsong Qiu1; Toshihiko Shimizu1; Nobuhiko Sarukura1; Masashi Yoshimura1; Tsuguo Fukuda2; Eduard Khutoryan3; Yoshinori Tatematsu3; Masahiko Tani3; Toshitaka Idehara3
1Osaka University, Japan; 2Fukuda Crystal Laboratory Co., Ltd, Japan; 3University of Fukui, Japan

We observed yellow light emission from ZnO single crystals with high conductivity by the irradiation of sub-terahertz waves from gyrotrons. The emitted spectrum has a broad peak around 2 eV. As the spatial distribution of yellow light reflects the gyrotron beam profile and is visible with bare eyes, the high-conductive ZnO single crystals may be applied as an imager of gyrotron beam patterns usable for quick beam diagnosis.

Terahertz Spectroscopy Of Engineered Stone

Miguel Ángel Báez; Borja Vidal
Universidad Politécnica de Valencia, Spain

In this work several brands of engineered stone composites have been studied in the terahertz band. The dielectric properties of the samples were determined using THz Time Domain Spectroscopy. Imaging of the internal stone patterns was performed as well. Results show different absorptions and refractive indexes for each brand which can be related to the different compounding processes employed. This study realizes the capability of terahertz radiation as a viable way of inspection of stone composites.

Dependence Of Terahertz Conductivity Of CNT-based Macroscale Films On The CNT Length And On Plasma Exposure Time

Sergey Zhukov1; Daria S. Kopylova2; Alexei Tsapenko2; Anna Mogogrychnaia1; Elena Zhukova1; Albert Nasibulin2; Boris Gorshunov1
1Moscow Institute of Physics and Technology, Russian Federation; 2Skolkovo Institute of Science and Technology, Russian Federation

Time-domain terahertz and infrared Fourier-transform spectroscopy techniques are used to study the conductivity mechanisms of free-standing macroscale thin films composed of disordered single-walled carbon nanotubes of two types -- of various tube's lengths and films treated with oxygen plasma. We observe and analyze change in the temperature dependence of the terahertz conductance from metal-type in films with long CNTs to semiconductor-type in films with short CNTs and similar behavior of the conductance of the films with increase in the plasma exposure time.

Study On Thermionic Emission Of A W-Y Alloy Cathode Applied In Magnetron

Shikai Qi1; Mingwei Hu2; Yang Gao1; Li Liu1; Wei Zeng1
1Institute of Electronics Engineering, Jiujiang University, China; 2School of Physics and Optoelectronics Engineering, Xidian University, China

A W-Y alloy cathode applied in magnetron tube has been developed. The thermionic emission experimental results show that the dc thermionic characteristic curve of the cathode has been straight up at 1500?br with no space charge deviation point. The lifetime experimental results show that the thermionic emission current density of the cathode decreases linearly from the initial 1.5A/cm2 to 0.2A/cm2 after 80h lifetime testing at 1600?br.

Unusual Ultrafast Photocarrier Dynamics In Type II Dirac Semimetal PtTe2 Thin Film In Terahertz Band
Guohong Ma; Peng Suo
Shanghai University, China

A type II Dirac semimetal PtTe2 thin film on YAG substrate was studied at room temperature by optial pump THz probe spectroscopy. After photoexcitation, an abrupt photoinduced positive THz photoconductivity (ÃZ"ÏÆ') occurs, which was developed into negative one within time scale of a few ps, and the negative ÃZ"ÏÆ' reaches the maximum at delay time of 10 ps. The subsequent relaxation of the negative ÃZ"ÏÆ' takes place within time scale of ~700 ps. The unusual photoexcitated relaxation reflects the dynamics of holes in Dirac cone and electrons beyond the linear cone in PtTe2 thin film after photoexcitation

Active Optically Controlled Broadband Terahertz Modulator Based On Fe3O4 Nanoparticles

Luyao Xiong1; Bo Zhang1; Hongyu Ji1; Wei Wang1; Xin Liu2; Jingling Shen1
1Capital Normal University, China ; 2Beijing Jiaotong University, China

In summary, we investigated an active optically-controlled broadband THz modulator based on Fe3O4 nanoparticles. The transmission of THz signals was modulated efficiently with an external CW laser to excite in the THz-TDS system. The modulation depth reached 92% under an external laser irradiance of 3.6 W/cm2 over a broad band (0.2--2.6 THz). The inner mechanism of this THz modulator was explained in detail by the high interface carrier densities of the hybrid structure. In addition, the limit modulated frequency of our device is ~12kHz. Thus, the results indicate that an active optically-controlled broadband THz modulator based on Fe3O4 nanoparticles was realized. The effective modulation and the ease of fabrication of our device demonstrate its wide application possibilities and its promising future in THz imaging and communication technologies.

Rotational Cuvette Measurements For Refractive Index Testing Using A THz Vector Network Analyser

Rhiannon Lees; Andreas Klein; Michael Cooke; Claudio Balocco; Andrew Gallant
Durham University, United Kingdom

This paper describes a new method for measuring the refractive index of liquids using a THz vector network analyser. The method relies on the change of optical path length in a rotating cuvette containing the liquid under test. The measured phase as a function of the cuvette angular displacement is used to calculate the refractive index of hexane, undecane and hexadecane, in the frequency range 0.8-1.05 THz.

Flexible THz Metamaterials Bonded To Paper For Chemical Sensing
Rhiannon Lees; Michael Cooke; Claudio Balocco; Andrew Gallant
Durham University, United Kingdom

We report on THz metamaterials for chemical sensing fabricated on low-loss, plastic, flexible substrates. The metamaterial is bonded to a paper sheet, which is wicked in the liquid to be analysed. Liquids with different dielectric constant result in a shift of the metamaterial resonant frequency, which can be detected by measuring its complex transmission using a THz vector network analyser, in the frequency range 0.75-1.1 THz.

Polarization Controlled Dual Resonant Tera-Hertz Transmission Through Asymmetric Aperture Array

Arnab Pattanayak1; Goutam Rana2; Ravi Kumar Jain1; Dipa Ghindani1; Arkabrata Bhattacharya1; Siddhartha P. Duttagupta2; Prasanna S. Gandhi3; Venu Gopal Achanta1; S S Prabhu1
1TIFR, C-225, FOTON LAB, India; 2IITB, EE Department, IIT Bombay, India; 3IITB, ME Department, Suman Mashruwala Lab, India

Resonant transmission of electromagnetic radiation through an array of rectangular apertures depends on two excited half-wavelength localized modes along the length and width of the aperture, respectively. However, due to dimension mismatch between length and width, the two excited modes do not spectrally coincide. In this paper, we conduct a study on periodic array of asymmetric aperture and demonstrate that introducing a taper along the long axis can yield both the modes simultaneously. Specifically, we show that, spectral peak positions and line-widths of these two modes can be tuned by just flipping the polarization from one state to its orthogonal state. Moreover, highly directive transmitted beam results at far field as the inter-element spacing of the aperture is reduced to half of the wavelength at resonance.

Optically Tunable Terahertz Notch Filter Based On Carbon Nanotubes

Daniel Gomon; Petr Demchenko; Victoria Soboleva; Egor Litvinov; Elizaveta Sheklanova; Mikhail Khodzitsky
ITMO University, Russian Federation

The tuning possibility of transmittance spectrum of CNT-based notch filter with cross-shaped geometry during optical pumping was shown.

Terahertz 1-bit Digital Dynamic Phase Programmable Metasurface Based On AlGaN/GaN Heterostructure

Hongxin Zeng1; Feng Lan1; ZiQiang Yang1; Yaxin Zhang1; Zongjun Shi1; Jing Yin1; Tianyang Song1; Pinaki Mazumder2
1Terahertz Research Centre, School of Electronic Science and Engineering, China; 2Department of Electrical Engineering and Computer Science, University of Michigan, United States

A terahertz 1-bit digital dynamic phase programmable metasurface (TDPM) consisting of a series of split-ring resonator (SRR) composite metamaterial with AlGaN/GaN hetero-structure as the element has been proposed to achieve dynamic beam steering and shaping. We experimentally validate the dynamic beam deflection of programmable metasurface under the different programming sequences. The terahertz beam deflects from -45Ã,° to -35Ã,° and 35Ã,° to 45Ã,° with the programming sequence 000111 and -33Ã,° to -26Ã,° and 26Ã,° to 33Ã,° with 00001111. The maximum deviation of the deflection angle is 2Ã,°. The experimental and experimental results are generally consistent with the theoretical results.

Photocontrol Phase Shifting With Extraordinary Optical Transmission Of Terahertz Waves Via Vanadium Dioxide Based Metasurface

Huajie Liang; Yaxin Zhang; Ziqiang Yang
University of Electronic Science and Technology of China, China

Here, we proposed a metasurface composed of metallic "I" structure in a hole and Vanadium Dioxide patches, which can achieve a photo induced phase shifting in Terahertz range. By combining the concepts of extraordinary optical transmission of subwavelength hole array with the dipolar resonant characteristics of the meta unit, this structure can achieve transmission resonant peak. Applying the phase transition of VO2, a continuous phase shift from 0ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,° to 76ÃfÆ'ââ,¬Å¡Ãfâ?sÃ,° near 0.69 THz with loss of about 3dB can be obtained within single layer structure in transmission mode.

Novel Hollow Core Antiresonant Terahertz Fiber With Metamaterial Cladding

Jakeya Sultana1; MD Saiful Islam1; Selim Habib2; Cristiano. M. B Cordeiro1; Alex Dinovitser1; Brian W.-H Ng1; Mayank Kowshik1; Heike Ebendorff-Heidepriem1; Derek Abbott1
1The University of Adelaide, Australia; 2The University of Central Florida, United States

We propose a novel low loss antiresonant (AR) terahertz fiber by means of a hollow core with metamaterial cladding. The propagation of fundamental and higher order modes are investigated using Finite Element Method (FEM) based software COMSOL, and the results are compared with standard AR fiber designs. Simulation results show that the novel metamaterial structure exhibits a transmission loss reduction of an order of magnitude compared to standard AR fibers, covering a single mode bandwidth (BW) of 700 GHz.

Terahertz Broadband Linear-to-circular Polarization Deflection Based On A Birefringent Reflective Metasurface

Jing Yin1; Feng Lan1; Ziqiang Yang1; Pinaki Mazumder2; Binglian Xiao1; Hongxin Zeng1; Luyang Wang1; Abdur Rauf Khan1
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; 2Department of Electrical Engineering and Computer Science, University of Michigan, United States

A terahertz broadband linear-to-circular (LTC) polarization deflection is proposed in this paper. By introducing a hybrid resonant structure with birefringent and broadband phase response, the polarizer can convert a linearly polarized (LP) wave to a circularly polarized (CP) wave with a deflection angle of 30Ã,°. In the 8.45% 3-dB axis ration (AR) bandwidth, the simulation results indicate that the average polarization conversion efficiency of the units reaches approximately 80% and the reflectance is 0.63 at 0.36 THz. The proposed polarization deflection has great potential application value in radar and wireless communication.

Slit Arrays For Plasmon-enhanced Vibrational Circular Dichroism: Characterization Of The Local Field Enhancement

Leonetta Baldassarre1; Francesco Mattioli2; Giuseppe Mazzeo3; Giovanna Longhi3; Sergio Abbate3; Giovanni Pellegrini4; Francesco Rusconi4; Michele Celebrano4; Marco Finazzi4; Lamberto Duò4; Chiara Zanchi5; Matteo Tommasini5; Marialilia Pea6; Sara Cibella6; Filippo Sciortino1; Alessandro Nucara1; Michele Ortolani1; Paolo Biagioni7
1Department of Physics, Sapienza University of Rome, Italy; 2Istituto Fotonica e Nanotecnologie CNR, Italy; 3Università degli studi di Brescia, Italy; 4Dipartimento di Fisica, Politecnico di Milano, Italy; 5Dip. di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, Italy; 6Istituto di Fotonica e Nanotecnologie (IFN) CNR, Italy; 7Department of Physics, Politecnico di Milano, Italy

We present mid-infrared arrays of resonant chiral plasmonic nanostructures (chiral slit pairs) that are designed to feature a strong circular dichroism and an enhanced near-field optical chirality. We fabricated both right- and left-handed arrays and characterized them by means of both reflection and transmission infrared spectroscopy. Moreover, as a preliminary step towards surface-enhanced vibrational circular dichroism experiments, we experimentally studied the local field enhancement within the individual slits.

A High-precision THz Beam Steering Array Applied 2-bit Non-uniform Coding Strategy By Fractionally Dividing The Phase Gradient Distribution

Luyang Wang1; Feng Lan1; Pinaki Mazumder2; Hongxin Zeng1; Ziqiang Yang1; Jing Yin1; Binglian Xiao1; Ziqi Zhang1; Zongjun Shi1
1School of Electronic Science and Engineering, University of Electronic Science and Technology of China, China; 2Department of Electrical Engineering and Computer Science, University of Michigan, United States

A novel 2-bit coding metasurface for terahertz beam steering is proposed here. By fractionally dividing the phase gradient distribution, a higher-precision beam steering has been implemented. Compared with uniform coding manner, the novel non-uniform coding strategy employed on the proposed metasurface can shorten prominently the step length of beam steering, highly being valued for high resolution imaging and detecting.

Frequency Selective Rasorber With Continuous Tunable Transmission Band Based On Varactor

Min Guo; Qiang Chen; Yuejun Zheng; Zhanshan Sun; Yunqi Fu
College of Electronic Science, College of Electronic Science, China

This paper proposed an active FSR which is based on varactor. Simulation results shows that the center of transmission window can be tuned from 9.87GHz to 11.22GHz, with loss less than 0.75dB, and there are steady wide band with reflection coefficient below -10dB extends from 5.65GHz to 15.39GHz. Since the total equivalent capacitance Ce of the resistive element is got by serial capacitance of double helix C and varactor Ct, and C is less than Ct in most cases. Thus, the total equivalent C cannot be changed in wide range. Thus, the transmission frequency cannot be changed in wideband. Therefore, the transmission window can be tuned in wideband is needed to studied in future research.

High-Performance And Low-Crosstalk Terahertz Plasmonic Crossings

Mingrui Yuan1; Ying Zhang1; Yongchang Lu1; Yanfeng Li1; Jianqiang Gu1; Jiaguang Han1; Weili Zhang2
1Tianjin University, College of Precision Instrument and Optoelectronic, Center for Terahertz Waves, China; 2Oklahoma State University, School of Electrical and Computer Engineering, United States

For terahertz integrated systems, an intersection between waveguides is inevitable and is often accompanied by considerable crosstalk and loss. Here, we propose and experimentally demonstrate a novel type of crossing with a footprint less than 0.2 mm×0.2 mm for terahertz surface plasmon polariton waveguiding. The crossing loss is estimated by investigating a sequence of waveguides with one, two and three crossings. By optimizing the crossover structure to suppress crosstalk, the measured loss is as low as -3.4 dB and the crosstalk is less than -19.12 dB/crossing at 0.55 THz. Furthermore, the relationship between crosstalk and crossing angle is discussed.

Radiation From Junctions Between Two-dimensional Plasmonic Waveguides
Oleksiy Sydoruk; Serhii Siaber; Simone Zonetti
Imperial College London, United Kingdom

There has been recent interest in the retardation regime of plasmon propagation in two-dimensional electron systems, when the plasmon and the light velocities are comparable to each other. The usual electrostatic approximation is no longer valid, and a plasmon incident upon a junction can scatter into radiation modes. Here, we will present theoretical analysis of junctions between two-dimensional plasmonic waveguides in the retardation regime and discuss (i) the plasmon scattering for different relationships between the plasmon and the free-space wavenumbers, (ii) numerical and approximate analytical solutions to the problem, (iii) implications of the result for the design of plasmonic devices.

Metal-graphene Stacking Structure For Dynamical Tunable Ultra-wide Band Absorbers

Renbin Zhong; Yan Liu; Yilin Lv; Chen Han; Wang Yiqing; Shenggang Liu
University of Electronic Science and Technology of China, China

By construction metal-graphene metamaterial with simple gold strips parallel or side-by-side arranged on a monolayer graphene as molecular cells, multi-band and ultra-wide band absorber can be achieved at mid-infrared frequencies. The extremely absorption bandwidth up to 11.8THz can be obtained, the intensity exceeds 90% at the absorption peak. Independently tunable multi-band and ultra-wide band absorber is also explored by stacking molecular cells with two or three layers. The results will benefit the integrated micro-structure research with flexible tunability, and the multilayer structure has potential applications in tunable filtering, sensing, cloaking objects and other multispectral devices.

X-Shaped Metamaterial Biosensor Combined With Microfluidic System For Different IPA Concentration Measurement

Shih Ting Huang1; Yu Ting Hu1; Ta Jeng Yen2; Da Jeng Yao2; Steve Hsu3; Kai-Yuan Tang3
1Department of Power Mechanical Engineering, National Tsing Hua University, Taiwan; 2National Tsing Hua University, Taiwan; 3ACE Biotek Co.,Ltd., Taiwan

X-shaped plasmonic biosensor (XPS) can have strong sensitivity within THz spectrum combined with microfluidic system. The microfluidic system can provide low volume reagents for detection, reduce noise from environment, and concentrate the sample on detection spots. TeraPulse 4000 equipment can be used for the measurement for biosensor, by observing variation of refractive index in THz frequency domain spectrum. The results show metamaterial device in comparison of different concentration of IPA, where refractive index reflects absorption of liquids. Furthermore, the effect of FOM and quality factor can be observed through resonant dip at designed 0.20898 THz.

Effects Of Substrate Phonon Absorption On The Resonance Properties Of Ultrathin Metamaterials In The Terahertz Range

Tianye Niu1; Boqi Qiu1; Ya Zhang2; Kazuhiko Hirakawa1
1Institute of Industrial Sicence, University of Tokyo, Japan; 2Tokyo University of Agriculture and Technology, Japan

We have investigated the reflection spectra of metal-insulator-metal (MIM) metamaterial absorbers (MMAs) in top-incidence and bottom-incidence configurations in terahertz (THz) frequency range. Top-incidence MIM MMAs show narrowband and large absorption, but no resonant mode is observed GaAs-based bottom-incidence MIM MMAs due to strong phonon absorption in GaAs substrate. 63% absorption peak is observed in Si-based bottom-incidence MIM MMAs, which becomes a good candidate for the integration with THz MEMS bolometer.

Multipole Terahertz Localized Plasmon Resonances On Spiral Structures

Vasily Gerasimov1; Sergey Kuznetsov2; Alexey Lemzyakov3; Ruslan Hafizov4
1Budker Institute of nuclear physics SB RAS, Russian Federation; 2Rzhanov Institute of Semiconductor Physics SB RAS, "TDIAM", Russian Federation; 3Budker Institute of nuclear physics SB RAS, Russian Federation; 4Novosibirsk State University, Russian Federation

Numerical simulations of sub-wavelength single and double logarithmic spiral metal disk array in the range of 0.04 - 5 THz have shown that high order localized surface plasmon resonances arise at oblique incidence and small gap sizes between the disks. The spectra and 2D distributions of the EM field at the resonant frequencies depend on the geometry of the structure, period of the array, and a gap between the disks in the doubled spiral structures, but there is no dependence on the twisting direction of the spirals.

Investigation Of The Reflectivity Spectra Of N-type GaN Semiconductor With Surface Relief Grating

Vytautas Janonis1; Pawel Prystawko2; Krzysztof Gibasiewic2; Jacek Kacperski2; Irmantas Kasalynas1
1Center for Physical Sciences and Technology, Lithuania; 2Institute of High Pressure Physics Polish Academy of Sciences, Poland

Reflectivity spectra of n-type GaN with a shallow or deep relief grating were investigated theoretically and experimentally in the spectrum range of 100-1500 cm-1. The surface Phonon-Plasmon-Polariton modes for the strong field confinement within GaN micro-cavities were engineered by proper selection of the periodicity, filling factor, and depth of the groves. Application of such surface relief gratings is important for the development of total power absorbers, filters, waveguides, and other types of optoelectronic devices.

Independent Linear Dual-polarization Terahertz Focusing At A Composite Multifunctional Metasurface

Wei Kou1; Yaxin Zhang1; Shixiong Liang2; Zhihong Feng1; Ziqiang Yang1
1Terahertz Science Cooperative Innovation Center, University of electronic science and technology, China; 2National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Ins, China

In this paper, we present a multifunctional metasurface enabling terahertz focusing for efficient terahertz wave control. Two different focal distances can be achieved under a normal incident wave with two different linear polarization. Further, the incident waves will form vertical or parallel axial focus with p(x) or s(y)-polarized component. In addition, this design method can be applied to other terahertz multifunctional devices which develops diversifications of the metasurface.

Enhanced Terahertz Smith-Purcell Radiation From Subwavelength Holes Array Within Metamaterials

Weihao Liu; Zijia Yu; Yucheng Liu; Qika Jia; Yalin Lu
University of Science and Technology of China, China

We propose to generate coherent terahertz radiation by using free-electron beams to excite arrays of rectangular sub-wavelength holes within metamaterials. The radiation is achieved due to the constructive interference of radiation from all sub-wavelength holes of the array via Smith-Purcell effect. Compared with that in conductor holes, the resonant modes in metamaterial holes have much higher intensity thanks to the excitation of terahertz surface plasmons. Thus, it can generate terahertz radiation with much higher intensity. Also, its radiating direction can be adjusted by changing the arrangement of the array. It offers a promising way of developing efficient and steerable terahertz sources.

Broadband Terahertz Modulator Based On Fin-line With Meta-atom

Xu Hou1; Ting Zhang2; Yaxin Zhang2; Ziqiang Yang2; Shixiong Liang3
1Terahertz Science Cooperative Innovation Center, China; 2Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology of, China; 3National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, China

In this paper, we present a broadband terahertz (THz) amplitude modulator by combining fin-line with meta-atom. The resonant mode of the meta-atom is controlled by the HEMT diode whose switch is controlled by the bias voltage. Consequently, the THz wave transmitted in the waveguide can be amplitude modulated. This terahertz modulator has a bandwidth of 60 GHz and relatively low insertion loss. This work may bring many potential applications for THz communication.

Phase Singularity In Double-layer Metamaterial Based On Lattice Resonance

Zhengli Han1; Seigo Ohno2; Hiroaki Minamide1
1Riken, Japan; 2Tohoku University, Japan

Electromagnetic wave experiences phase changing both in propagation and resonance. Extreme phase changing is interesting and has its applications. Here we report a phase singularity phenomenon in double-layer metamaterial.

Terahertz Chemical Sensor Based On The Plasmonic Hexagonal Microstructured Holes Array In Aluminum

ABHISHEK PANGHAL; Ravi Kumar Jain; Arnab Pattanayak; Arkabrata Bhattacharya; Venu Gopal Achanta; Shriganesh Prabhu
Tata Institute of Fundamental Research, India

Terahertz Chemical sensor based on the hexagonal microstructure air holes in a free-standing Aluminum foil having a thickness ~ 11 µm has been designed by numerical simulations which are further optimized and fabricated by Computerized Numerical Control (CNC) drilling machine. Localized plasmons (LPs) excited at the air holes are used to demonstrate refractive index sensing for liquids. The proposed sensor would be a potential device for liquid sensing applications.

Topologically Protected Tera-Hertz Loop Yagi-Uda Absorber