TST, Vol. 7, No. 2, PP. 53-69
(Invited paper) Terahertz time-domain spectroscopy of absorbing materials and of metamaterials
J.-L. Coutaz 1*, M. Bernier 1, F. Garet 1, S. Joly 1,a , Y. Miyake 2, H. Minamide 2, E. Lheurette 3, and D. Lippens 3
1 IMEP-LAHC, UMR CNRS 5130, University of Savoie, 73376 Le Bourget du Lac Cedex, France
2 RIKEN, Center for Advanced Photonics, Aoba-ku, Sendai, Miyagi 980-0845, Japan
3 IEMN, UMR CNRS 8520, Avenue Poincaré, CS 60069, 59652 Villeneuve d’Ascq Cedex, France
a) Present address: IMS, University of Bordeaux, France
*1 Email: coutaz@univ-savoie.fr
(Received January 2, 2014)
Abstract: This paper gives a review of recent works we performed in view of characterizing natural materials and metamaterials by terahertz time-domain spectroscopy. We address materials that exhibit a low transmittance in given narrow spectral bands or over the whole experimental spectral window. We give rules to select the most adapted technique for a precise characterization of the sample, i.e. for determining with the best precision the refractive index as well as the coefficient of absorption of the material of the tested sample. The procedures are validated and illustrated by examples of characterization of materials like maltose and DAST, and of fishnet metamaterials that exhibit a left-handed character or a chiral behaviour.
Keywords: Terahertz time-domain spectroscopy, Metamaterials.
doi: 10.11906/TST.053-069.2014.06.05
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TST, Vol. 7, No. 2, PP. 70-79
(Invited paper) The development of gyrotrons and their applications for plasma science and material processing
Yuri V. Bykov 1, Naum S. Ginzburg 1, 2, Mikhail Yu. Glyavin 1*, 2, Sergey V.Golubev 1, Grigory G. Denisov 1, Alexey G.Luchinin 1, Vladimir N.Manuilov 2 and the IAP RAS - GYCOM team
1 Institute of Applied Physics of the Russian Academy of Sciences, GYCOM Ltd. 46 Ul'yanov St., 603950 Nizhny Novgorod, Russia
2 Nizhny Novgorod State University, 23 Gagarin Ave., 603950 Nizhny Novgorod, Russia
*1 Email: glyavin@appl.sci-nnov.ru
(Received January 16，2014)
Abstract: The data about gyrotron-based technological systems and THz-band gyrotrons for diagnostics of different media are presented. The possible improvements of selective excitation of the operating modes with allowance for the competition with lower harmonics are considered. Double-beam electron optics is developed for a THz- band gyrotron. A sheet gyrotron as a tool for combining a high output power and frequency tuning is discussed. Long-life cathodes with additional heating by reflected electrons are preliminarily tested. 3D calculation of gyrotron operation regimes is carried out and the azimuthal inhomogeneity effects are analyzed. The results of experimental tests of a pulsed 200-kW/670-GHz gyrotron used for the initiation of localized gas discharge are presented.
Keywords: Gyrotron, Material processing, Terahertz, Multi-beam electron gun, Pulse field, Plasma discharge
doi: 10.11906/TST.070-079.2014.06.06
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TST, Vol. 7, No. 2, PP. 80-99
(Invited paper) Mode splitting in the terahertz functional devices: a review
Lin Chen, Yiming Zhu * and Songlin Zhuang
Shanghai Key Lab of Modern Optical System, Engineering Research Center of Optical Instrument and System, Ministry of Education, University of Shanghai for Science and Technology,
516, Jungong Rd. Yangpu Dist. Shanghai, China, 200093
* Email: ymzhu@usst.edu.cn
(Received January 20, 2014)
Abstract: The mode splitting effect was observed widely in different waveguide structures in Terahertz (THz) field and has great potentiality to achieve the high quality THz functional devices. This review discusses various THz functional waveguide devices based on mode splitting and analyzes the physical origins of such phenomena.
Keywords: Terahertz functional device, Mode splitting, Frequency selective surface
doi: 10.11906/TST.080-099.2014.06.07
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TST, Vol. 7, No. 2, PP. 100-107
Evaluation of surface carrier recombination of optically excited silicon using terahertz time-domain spectroscopy
K. A. Salek, K. Takayama, I. Kawayama *, H. Murakami and M. Tonouchi
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
* Email: kawayama@ile.osaka-u.ac.jp
(Received February 14, 2014)
Abstract: In this study, the properties of optically excited silicon were investigated using terahertz time-domain spectroscopy (THz-TDS). The surface was illuminated with 365-nm ultraviolet (UV) light to excite charge carriers, and properties such as conductivity, charge carrier density and mobility were evaluated. The illumination effect significantly changed the conductivity as well as the surface recombination velocity (SRV) by altering the surface potential via photoexcited carriers. The SRV observed on the silicon surface varied from 1.56×104 to 3.45×103 cm/s, indicating that UV illumination greatly reduced the SRV depending on the photoexcited carrier density at the silicon surface.
Keywords: Terahertz spectroscopy, Silicon, UV light illumination, Surface recombination velocity
doi: 10.11906/TST.100-107.2014.06.08
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