International Journal of Terahertz Science and Technology
Vol.5, No.2, June 2012. PP.67-113 (4)
date2012-06-29 23:48:34 Click No.5671

TST, Vol. 5, No. 2, PP. 67-77

(Invited Paper) THz Gyrotrons: Status and Possible Optimizations

Mikhail Yu. Glyavin 1*, Naum S. Ginzburg 1, Arkady L. Goldenberg 1, Gregory G. Denisov 1, Alexey G.Luchinin 1, Vladimir N.Manuilov 2, Vladimir E. Zapevalov 1, Irina V. Zotova 1
1
Institute of Applied Physics Russian Academy of Science, 603950, 46 Ul'yanov St., Nizhny Novgorod, Russia
2 Nizhny Novgorod State University, 603950, 23 Gagarin Av., Nizhny Novgorod, Russia
*1 Email:
glyavin@appl.sci-nnov.ru

(Received April 03, 2012)

Abstract: The state of the art of THz gyrotrons is briefly discussed. The possible optimizations of the magnetron injection gun and electrodynamics system for THz gyrotrons are discussed. The electron optical systems with extraction of reflected electrons are presented. The significant increasing of electrons transverse energy predicted in theory and confirmed by experiments. In order to increase the integral output power, it is suggested using a planar gyrotron scheme with a high oversized factor. The results of nonlinear dynamics simulation show that in such scheme it is possible to reach an output power of several hundred kilowatts at sub-THz band with a fine frequency tuning by changing the distance between plates.

Keywords: Terahertz, Gyrotron, Electron gun with extraction of reflected electrons, Planar scheme

doi: 10.11906/TST.067-077.2012.06.06

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TST, Vol. 5, No. 2, PP. 78-86

(Invited Paper) THz Generation Using Cherenkov Phase Matching

Kei Takeya 1*, Koji Suizu 2 and Kodo Kawase 1, 3
1
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
2 Chiba Institute of Technology, Tsudanuma, Narashino, Chiba, Japan
3 RIKEN, Aramaki-aoba, Aoba-ku, Sendai, Japan
*1 Email:
takeya@nuee.nagoya-u.ac.jp

(Received June 25, 2012 )

Abstract: An efficient terahertz (THz) wave generation based on Cherenkov type radiation from non-linear optical (NLO) crystals is presented in this paper. In terms of the THz generation from NLO crystals, it is well known that the high absorptivity and the phase mismatch prevent the effective THz generation. Using Cherenkov type THz radiation, we solved the problems and obtained an advantage that many crystals can be used as THz wave emitters. The successful generation of monochromatic THz waves is demonstrated with wide tunability in the range 0.2C3.0 THz. We obtained the enhancement factor of about 50 as a result of a suppression of phase miss-matching with surfing configuration for bulk NLO crystal. In addition, using prism-coupled Cherenkov phase-matching (PCC-PM) method with the organic crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST), we achieved THz-wave radiation with wide-tunability with no deep absorption features. The obtained spectra did not depend on the pump wavelength.

Keywords: Cherenkov phase matching, LiNbO3, Terahertz, prism-coupled Cherenkov phase-matching (PCC-PM)

doi: 10.11906/TST.078-086.2012.06.07

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TST, Vol. 5, No. 2, PP. 87-96

(Invited Paper) Resonant Field Enhancement in Hybrid Plasmonic Geometries

Xinchao Lu 1*, 2, Li Wang 2, Weili Zhang 1
1 School of Electrical and Computer Engineering, Oklahoma State University,
Stillwater, Oklahoma 74078, USA
2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese
Academy of Sciences, PO Box 603, Beijing 100190, People¨s Republic of China
*1 E-mail:
xinchao@iphy.ac.cn

(Received May 29, 2012)

Abstract: We report an anomalous field enhancement of terahertz transmission in metallic, hybrid plasmonic geometries. The integration of a rectangle particle in the hole not only results in an eight times normalized transmittance compared to that of the hole-only counterpart, but also tailors polarization-dependent transmission discrepancy encountered in arrays of rectangular holes. In addition, plasmonic structures made of metallic rings integrated into the subwavelength holes are investigated. The emergence and the interplay of various resonances sustained by the hybrid plasmonic samples are elucidated. To reveal a coherent physical picture, relevant dimensions of the samples are modified and their impact on the resonance properties is analyzed. The understanding of the interplay of various resonances will foster applications which require plasmonic substrates to exhibit simultaneously resonances at well-defined frequencies and line widths.

Keywords: Terahertz frequencies, Surface plasmons, Enhanced transmission

doi: 10.11906/TST.087-096.2012.06.08

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TST, Vol. 5, No. 2, PP. 97-113

Analysis of Photo-Irradiated Double-Drift Region Silicon Impact Avalanche Transit Time Devices in the Millimeter-wave and Terahertz Regime

Aritra Acharyya 1* and J. P. Banerjee 1
1
Institute of Radio Physics and Electronics, University of Calcutta, 92, APC Road, Kolkata 700009, India.
*1 E-mail:
ari_besu@yahoo.co.in

(Received May 08, 2012; accepted June 17, 2012)

Abstract: Effect of photo-irradiation on the avalanche response time of Millimeter-wave (mm-wave) and Terahertz (THz) Double-Drift Region (DDR) Silicon Impact Avalanche Transit Time (IMPATT) devices is investigated in this paper. A model to study the photo-irradiation effect on the DC and high-frequency properties of the mm-wave and THz IMPATTs is developed by the authors based on which the simulation is carried out to calculate the avalanche response time of 94, 140, 220 GHz and 0.3 THz DDR Silicon IMPATTs under two different optical illumination configurations (Top Mount (TM) and Flip Chip (FC)). It is interesting to observe that the DC and high-frequency parameters of the device are more sensitive to electron dominated photo current (TM structure) compared to the hole dominated photo current (FC structure). Results show that the avalanche response time of the device decreases due to optical illumination on both TM and FC structures and percentage of decrease in avalanche response time in TM structure is higher as compared to that in FC structure. Larger decrement of avalanche response time due to optical illumination in TM structure causes larger deviation of phase shift between RF voltage and terminal current of the device from 1800 which is the ideal phase difference between current and voltage for maximum RF power output; this is the main cause of greater reduction in RF power output in TM structure compared to FC structure due to optical illumination.

Keywords: Avalanche response time, DDR IMPATT device, Flip chip, Top mount, Terahertz regime.

doi: 10.11906/TST.097-113.2012.06.09

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