Abstract-Enhanced Terahertz Wave Generation from Cytop Antireflection–Coated DAST Crystal

Hirohisa Uchida, Chisa Koyama, Takeshi Takagi, Pei-bin Wang, Takayuki Kamei, Saroj R. Tripathi, Kodo Kawase, Kei Takeya

https://link.springer.com/article/10.1007/s10762-020-00674-6

There was no appropriate antireflection coating material for organic nonlinear optical (NLO) crystal used for terahertz wave generation; therefore, it was difficult to reduce Fresnel’s reflection loss of laser power used to excite the emitter crystal until we found that an amorphous polymer “Cytop” was applicable. Here, we demonstrate enhanced terahertz (THz) wave generation from an organic NLO crystal using a coating made from Cytop. With the Cytop coating, surface reflection losses of the excitation light were minimized, resulting in a significant improvement in THz wave generation over a wide frequency range.

Abstract-Pump wavelength-independent broadband terahertz generation from a nonlinear optical crystal

Kei Takeya, Koutarou Okimura, Kengo Oota, Kodo Kawase, and Hirohisa Uchida

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-17-4100

In nonlinear optical (NLO) crystals, the selection of pump light wavelengths for the generation of terahertz (THz) waves is limited due to problems associated with coherence length, refractive index, and absorption by the crystal. Relaxation of this limitation would open up potential light sources for THz generation. One such solution, Cherenkov phase matching, removes the coherence length constraint. In this study, we attempted to generate THz waves from an NLO crystal using femtosecond pulses of various wavelengths. Specifically, 805-nm and 1560-nm femtosecond pulses were used to pump a prism-coupled LiNbO3${\mathrm{LiNbO}}_3$ crystal. Broadband THz-wave generation and a THz-wave output proportional to the square of the pump light intensity were observed at both wavelengths. The generation of THz waves by prism-coupled Cherenkov phase matching was not limited by the wavelength of the pump light. Moreover, THz-wave generation at even greater intensities may be possible by optimizing the pump source and coupling to an NLO crystal.

© 2018 Optical Society of America

US Patent-Terahertz wave measuring device, measuring method, and measuring rig

United States Patent 9784610
Inventor:
Uchida, Hirohisa (Kyoto, JP) 

http://www.freepatentsonline.com/9784610.html

There is provided a terahertz wave measuring device including (1) a terahertz wave generation element that generates a terahertz wave by difference frequency generation based on excitation light that is incident to the terahertz wave generation element, the excitation light including a plurality of different wavelength components and being condensed so as to have a beam diameter of a predetermined size, (2) a structural body through which the terahertz wave is transmitted; and (3) a detector that detects an intensity of the terahertz wave that has been transmitted through the structural body, wherein the structural body includes a sample holder of a predetermined width that holds a sample, and the structural body is in close contact with or is joined to the terahertz wave generation element.