TST, Vol. 1, No. 2, PP. 51-64
GaN-based Semiconductor Devices for Terahertz Technology
Yue Hao, Lin-An Yang * and Jin-Cheng Zhang
Key Lab of Wide Band Gap Semiconductor Materials and Devices,
Xidian University, Xi¡¯an, 710071, China
* Email: layang@xidian.edu.cn
Abstract£ºThe advantages of the properties of GaN over traditional III-V materials are discussed for applications in terahertz (THz) regime. Consequently the GaN-based devices which include electronics and photonics devices are investigated with emphases on the theoretical and practical developments of Quantum Cascade Lasers, Plasma Wave FETs and Negative Differential Resistance diodes. The results demonstrate that GaN is a promising material for THz semiconductor devices with an excellent performance in operating temperature, frequency and output power. It is found that the dislocations in GaN crystal seriously impact on the performance of THz devices. It is also shown that a great progress of MOCVD technique gives the potential in GaN epitaxial growth for THz applications. Finally, our recent jobs in GaN fabrication are revealed to demonstrate the further researches in THz regime.
Keywords: Terahertz, GaN, Quantum cascade laser, Plasma wave, Negative differential resistance.
doi: 10.11906/TST.051-064.2008.06.07
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TST, Vol. 1, No. 2, PP. 65-72
Quasi-Optical Components for High Power Wave Beam Control
M.I.Petelin
Institute of Applied Phisics, Russian Academy of Sciences, 46, Ulianov Street,
603600 Nizhny Novgorod, Russia
Phone +7(831)4365921, Fax +7(831)4160616,
Email: petelin@appl.sci-nnov.ru
Abstract: This paper summarizes the simplest methods applicable to transmission and control of intense coherent electromagnetic radiation at frequencies near and within the THz band.
Key words: Intense microwave beams, Oversized structures
doi: 10.11906/TST.065-072.2008.06.08
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TST, Vol. 1, No. 2, PP. 73-99
10 MW, 0.14 THz, CW Gyrotron and Optical Transmission System for Millimeter Wave Heating of Plasmas in the Stellarator W7-X
M.Thumm *, G. Dammertz, G. Gantenbein, S. Illy, S. Kern, W. Leonhardt, G. Neffe, B. Piosczyk, M. Schmid
Forschungszentrum Karlsruhe, Association Euratom-FZK,
Institut f¨¹r Hochleistungsimpuls- und Mikrowellentechnik,
Postfach 3640, 76021 Karlsruhe, Germany
* Universität Karlsruhe, Institut f¨¹r Höchstfrequenztechnik und Elektronik,
Kaiserstr. 12, 76131 Karlsruhe, Germany
* Email: manfred.thumm@ihm.fzk.de
H. Braune, V. Erckmann, F. Hollmann, L. Jonitz, H.P. Laqua, G. Michel, F. Noke, F. Purps, T. Schulz, M. Weissgerber
Max-Planck-Institut f¨¹r Plasmaphysik (IPP),
Wendelsteinstr. 1, 17491 Greifswald, Germany
P. Brand, M. Gr¨¹nert, W. Kasparek, H. Kumric, C. Lechte, B. Plaum
Institut f¨¹r Plasmaforschung, Universität Stuttgart,
Pfaffenwaldring 31, 70569 Stuttgart, Germany
Abstract: Electron cyclotron heating (ECH) has proven to be one of the most attractive heating schemes for stellarators, as it provides net current free plasma start up and heating. Both, the stellarator Wendelstein 7-X (W7-X), which is under construction at IPP-Greifswald, Germany, and the ITER tokamak, which will be built at Cadarache, France, will be equipped with a strong EC-heating and current drive system. Both systems are comparable in frequency and have CW (continuous wave) capability (0.14 THz, 10 MW for W7-X and 0.17 THz, 24 MW for ITER). The commissioning of the ECH plant for W7-X is well underway, the status of the project and first integrated full power test results from two modules are reported and may provide valuable input for the ITER plant. The 10 gyrotrons at W7-X will be arranged in two sub-groups symmetrically to a central beam duct in the ECH hall. The RF-wave of each subgroup will be combined and transmitted by a purely optical multibeam wave guide transmission line (copper mirrors) from the gyrotrons to the plasma torus. The combination of the 5 gyrotron beams to two beam lines each with a power of 5 MW reduces the complexity of the system considerably. The single-beam as well as the multi-beam waveguide mirrors and the polarizers have been already manufactured. Cold tests of a full size uncooled prototype line delivered an efficiency exceeding 90%. The mm-wave power will be launched to the plasma through ten synthetic-diamond barrier windows and in-vessel quasi-optical plug-in launchers allowing each 1 MW RF-beam to be steered independently. The polarization as well as the poloidal and toroidal launch angle will be adjusted individually to provide optimum conditions for different heating and current drive scenarios. The first series gyrotrons were tested and yielded a total output power of 0.98 MW, with an efficiency of 31% (without a single-stage depressed collector) in short-pulse operation and of 0.92 MW in pulses of 1800 s (efficiency of almost 45% at a depression voltage of 29 kV). The Gaussian mode output power was 0.90 MW and the power measured in a calorimetric load after a 25-m-long quasi-optical transmission line (seven mirrors) was 0.87 MW.
Keywords: Electron cyclotron heating, Fusion plasmas, Stellarator, High power CW gyrotron, Quasi-Optical transmission.
doi: 10.11906/TST.073-099.2008.06.09
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TST, Vol. 1, No. 2, PP. 100-106
Development of THz gyrotrons and application to high power THz technologies
T. Idehara, I. Ogawa, T. Saito, S. Mitsudo, Y. Tatematsu, La Agusu H. Mori and S. Kobayashi
Research Center for Development of Far Infrared Region, University of Fukui (FIR FU),
3-9-1 Bunkyo, Fukui-shi 910-8507, Japan
Email: idehara@fir.fukui-u.ac.jp
Abstract: A gyrotron with a 21 T pulse magnet achieved the breakthrough of 1 THz. This is the first result of high frequency operation in the world beyond 1 THz. In addition, new gyrotron series in FIR FU, University of Fukui, so-called Gyrotron FU CW Series is being developed. Such a present status of high power THz radiation sources - gyrotrons in FIR FU and their application to high power THz technologies will be introduced.
Keywords: THz source, Gyrotron, High power THz technologies
doi: 10.11906/TST.100-106.2008.06.10
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TST, Vol. 1, No. 2, PP. 107-125
Research Highlights from the Novosibirsk 400 W average power THz FEL
G. N. Kulipanov, N.G. Gavrilov, B.A. Knyazev, E.I. Kolobanov, V.V. Kotenkov, V.V. Kubarev, A.N.
Matveenko, L.E. Medvedev, S.V. Miginsky, L. A. Mironenko, V. K. Ovchar, V.M. Popik, T.V. Salikova,
M.A. Scheglov, S.S. Serednyakov, O.A. Shevchenko, A.N. Skrinsky, V.G. Tcheskidov, N.A. Vinokurov
Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia
M.A. Demyanenko, D.G.Esaev, E.V. Naumova, V.Y. Prinz
Rzhanov Institute of Semiconductor Physics, 630090 Novosibirsk, Russia
V.P. Fedin
Nikolaev Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia
A.M.Gonchar, S.E. Peltek,
Institute of Cytology and Genetics, 630090 Novosibirsk, Russia
A.K. Petrov,
Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk, Russia
L.A. Merzhievsky
Lavrentyev Institute of Hydrodynamics, 630090 Novosibirsk, Russia
V.S. Cherkassky
Novosibirsk State University, 630090 Novosibirsk, Russia
Abstract: The first stage of the Novosibirsk high power free electron laser (NovoFEL) was commissioned in 2003. It is a CW FEL based on non-superconducting, low-frequency (180 MHz) single-pass accelerator-recuperator with the following parameters: the electron energy is 12 MeV; charge per bunch is 1,5 nC; the bunch repetition rate is 5.6 to 22.5 MHz; the maximum average current is 30 mA; the bunch duration is 40 to 100 ps. The radiation spectral range is 110 - 240 ¦Ìm at the first harmonics, 60 - 117 ¦Ìm and 40 - 80 ¦Ìm at the second and third harmonics correspondingly. The maximum average power is up to 0.4 kW for the first harmonics. The maximum average power of the second and third harmonics is 2% and 0.6% with respect to the first harmonics. The maximum peak power is 1 MW, and the repetition frequency is 5.6 and 11.2 MHz. The relative spectral width is 0.25 ¨C 1%. The radiation is completely spatial coherent, and the degree of linear polarization of radiation is better than 99.6 %.Laser radiation is transmitted through nitrogen-filled optical beamline to the experimental hall. To provide ultrahigh vacuum in the FEL and accelerator-recuperator, their vacuum volume is separated from the beamline by a diamond window. Four user stations (the diagnostic station, the photochemistry station, the biological station, and the THz imaging station) are in operation now. Two other stations are under construction: the station for introscopy and spectroscopy, and the aerodynamics station. The high average power of the FEL enables development of imaging techniques. Several methods for two-dimensional visualization of THz radiation, including an uncooled microbolometer camera for THz high-speed imaging with a time resolution of 1 to10-2 s, have been developed. Instrumentation for the experimental station is developed and tested (windows, beam splitters, pyroelectric detectors, bolometers, Fresnel zone plates, and kinoform lenses). During the last year the NovoFEL was operating as a user facility. Soft ablation of biological molecules under terahertz radiation has been studied at the NovoFEL during the last three years. Precisely tuning radiation energy, one can achieve the regime when ¡°biological¡± molecules (DNA, proteins, etc) are ¡°evaporated¡± without defragmentation. These results can lead to creation of new biotechnologies. Experiments in physics, chemistry, biology, condensed matter and technology at four user stations are surveyed in this paper. Next year we plan to commission the second stage of the NovoFEL, based on the four-track 40 MeV accelerator-recuperator, using the same accelerating RF structure as the first stage. The FELs in the second and fourth tracks are to generate radiation in the spectral ranges of 5-30 ¦Ìm and 30-100 ¦Ìm, respectively. The expected power of each FEL is more than 1 kW.
Keywords: THz FEL, Novosibirsk high power free electron laser
doi: 10.11906/TST.107-125.2008.06.11
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