Abstract-Effective Terahertz Wave Parametric Generation Depending on the Pump Pulse Width Using a LiNbO 3 Crystal

 Kouji Nawata ;  Shin'ichiro Hayashi ;  Hideki Ishizuki ;  Kousuke Murate , Kazuki Imayama,  Yuma Takida,   Vincent Yahia,  Takunori Taira,  Kodo Kawase,  Hiroaki Minamide

http://ieeexplore.ieee.org/document/7984855/

Injection-seeded terahertz (THz)-wave parametric generation pumped by subnanosecond pulses was demonstrated as an exploration of the effective pump pulse width. In experiments, pump sources with different pump widths of 35–850 ps were used. The relationship between the undesirable effect of stimulated Brillouin scattering (SBS) and the THz-wave output in LiNbO 3 was analyzed. The transient effect on SBS was not actualized around the acoustic phonon lifetime of LiNbO 3 . Pump widths below 420 ps were found to provide THz-wave generation with an energy conversion efficiency of 10−4. With a pump width of 700 ps, which is around five phonon lifetimes, the conversion efficiency was decreased about one order of magnitude from that of the pump width of 420 ps. Additionally, the peak power of the THz-wave output was maintained at about 15 kW with an actual range of 10–20 kW below 200 ps. A continuous change in the THz-wave pulse energy was obtained for six-fold energy scaling from 100 to 600 nJ.

Non-destructive drug inspection in covering materials using a terahertz spectral imaging system with injection-seeded terahertz parametric generation and detection

Mikiya Kato,1 Saroj R. Tripathi,1,* Kosuke Murate,1 Kazuki Imayama,1 and Kodo Kawase1,2

 Graduate School of Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya, 464-8603 Japan 2 RIKEN, 519-1399, Aramaki-Aoba, Aoba, Sendai 980-0845, Japan
 * tripathi@nuee.nagoya-u.ac.jp

https://www.osapublishing.org/view_article.cfm?gotourl=https%3A%2F%2Fwww%2Eosapublishing%2Eorg%2FDirectPDFAccess%2FCA54CE12-0741-BABF-8F2A4AF83A0398A0_338151%2Foe-24-6-6425%2Epdf%3Fda%3D1%26id%3D338151%26seq%3D0%26mobile%3Dno&org=

Abstract: In 2003, we reported the first-ever development of a spectral imaging system for illicit drugs detection using a terahertz (THz) wave parametric oscillator (TPO) [K. Kawase et al., Opt. Exp. 11(20), 2549 2003]. The system has a dynamic range below four orders of magnitude, which enables it to identify reagents only through thin envelopes using spectral imaging. Recently, we succeeded in developing a high power and high sensitivity THz wave spectral imaging system using injection-seeded THz parametric generation and detection. A dynamic range in excess of 80 dB has been obtained, which is much higher than that of the 2003 system. In this study, the new spectral imaging system successfully identified reagents through thicker material than the thin envelopes used previously.
 ©2016 Optical Society of America

Abstract-Terahertz wave three-dimensional computed tomography based on injection-seeded terahertz wave parametric emitter and detector

Saroj R. Tripathi, Yuya Sugiyama, Kosuke Murate, Kazuki Imayama, and Kodo Kawase

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-6-6433

We demonstrate a high dynamic range, three-dimensional (3-D) terahertz (THz) wave computed tomography system in which frequency tunable, Fourier transform-limited, high-power THz waves are emitted by an injection-seeded parametric source and ultrasensitive detection of THz waves is accomplished by heterodyne detection. This system covers the frequency range of 0.95 to 2.7 THz and has a maximum dynamic range in excess of nine orders of magnitude, enabling the acquisition of high-resolution 3-D tomographic images of samples with strong THz absorption. As an illustration, we obtained 3-D computed tomographic images of a pencil and a plastic product with an internal defect that demonstrates the potential applications of our imaging system in non-destructive testing and evaluation of industrial products.

© 2016 Optical Society of America

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