Showing posts with label Mitsuharu Shiwa. Show all posts
Showing posts with label Mitsuharu Shiwa. Show all posts

Monday, November 14, 2016

Abstract-Polarization-variable emitter for terahertz time-domain spectroscopy




Dmitry S. Bulgarevich, Makoto Watanabe, Mitsuharu Shiwa, Gudrun Niehues, Hideaki Kitahara, and Masahiko Tani
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-24-27160

We report on the progress in the development of linear polarization-variable multi-electrode emitters for terahertz time-domain spectroscopy. The results on its microfabrication, the finite element method modeling of appropriate bias distribution between electrodes, the finite-difference time-domain simulated spectral output, and actual experimental testing are presented. The rotation of the emitted terahertz field with linear polarization on an angle multiple of 45° can be achieved by synchronized bias and single polarizer rotations.
© 2016 Optical Society of America
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Wednesday, June 10, 2015

Abstract-A matter of symmetry: terahertz polarization detection properties of a multi-contact photoconductive antenna evaluated by a response matrix analysis



Gudrun Niehues, Stefan Funkner, Dmitry S. Bulgarevich, Satoshi Tsuzuki, Takashi Furuya, Koji Yamamoto, Mitsuharu Shiwa, and Masahiko Tani
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-12-16184


While terahertz time domain spectroscopy (THz-TDS) is a well-established technique, polarization sensitive measurements are challenging due to the need of broadband polarization devices. Here, we characterize our recently introduced multi-contact photoconductive detector antenna with a response matrix analysis. We show that the lead lines attached to electrodes reduce the antenna symmetry and thereby influence the properties of the response matrices. With a wire grid polarizer, we simulate a sample influencing the polarization angle and the intensity of the incident THz pulse. Evaluating the measurements with the response matrix analysis, our results show a well agreement of the adjusted and measured polarization angles and intensities over a frequency range from 0.25 to 0.8 THz.
© 2015 Optical Society of America
Full Article  |  PDF Article

Tuesday, April 22, 2014

Abstract-A polarization-sensitive 4-contact detector for terahertz time-domain spectroscopy




Dmitry S. Bulgarevich, Makoto Watanabe, Mitsuharu Shiwa, Gudrun Niehues, Seizi Nishizawa, and Masahiko Tani  »View Author Affiliations


Optics Express, Vol. 22, Issue 9, pp. 10332-10340 (2014)
http://dx.doi.org/10.1364/OE.22.010332
http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-9-10332
A light polarization angle-sensitive photoconductive detector for terahertz time-domain spectroscopy is computer-modeled, microfabricated, and tested. The experimental results show good agreement with the linear angular response for an ideal detector. The detector’s frequency, angular, and crosstalk responses are discussed in the context of theoretical and experimental considerations.
© 2014 Optical Society of America