Abstract-High-Speed Terahertz Waveform Measurement for Intense Terahertz Light Using 100-kHz Yb-Doped Fiber Laser

Masaaki Tsubouchi, Keisuke Nagashima,

http://www.mdpi.com/1424-8220/18/6/1936/htm

We demonstrate a high-speed terahertz (THz) waveform measurement system for intense THz light with a scan rate of 100 Hz. To realize the high scan rate, a loudspeaker vibrating at 50 Hz is employed to scan the delay time between THz light and electro-optic sampling light. Because the fast scan system requires a high data sampling rate, we develop an Yb-doped fiber laser with a repetition rate of 100 kHz optimized for effective THz light generation with the output electric field of 1 kV/cm. The present system drastically reduces the measurement time of the THz waveform from several minutes to 10 ms.

Abstract-Mechanism of relativistic Doppler reflection from a photoinduced moving plasma front studied by terahertz time-domain spectroscopy

Nanase Kohno, Ryuji Itakura, and Masaaki Tsubouchi

We applied terahertz (THz) time-domain spectroscopy to reveal the mechanism of the relativistic Doppler reflection of THz light from a photoinduced plasma front in a silicon wafer. The frequency upshift caused by the Doppler reflection was identified by measurement of the reflected THz waveforms and compared to the calculated results obtained using the one-dimensional finite-difference time-domain method. The relation between the energy density of the pump light and the frequency upshift was also explored. We found that the interaction time of the moving plasma front and the reflected THz pulse is a key factor in understanding the mechanism of the relativistic Doppler reflection.

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Abstract-Contact grating device with Fabry–Perot resonator for effective terahertz light generation

Masaaki Tsubouchi, Keisuke Nagashima, Fumiko Yoshida, Yoshihiro Ochi, and Momoko Maruyama  »View Author Affiliations

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-18-5439

Optics Letters, Vol. 39, Issue 18, pp. 5439-5442 (2014)
http://dx.doi.org/10.1364/OL.39.005439

A novel design for a contact grating device with an incorporated Fabry–Perot resonator is proposed for high-power terahertz (THz) light generation. We deposited a multilayer consisting of Ta2O5 and Al2O3 on a magnesium-doped stoichiometric LiNbO3 substrate and fabricated grating grooves on the outermost layer. The multilayer was designed such that conditions for a Fabry–Perot resonator were satisfied for light diffracted by the grating. Consequently, the fraction of light transmitted into the LiNbO3 substrate, i.e., the diffraction efficiency, was enhanced by the resonator. The diffraction efficiency of the fabricated device was 71%, which is close to the calculated value of 78% from the optimized design. THz light generation was also demonstrated with the contact grating device. The THz output of 0.41 μJ was obtained using near-infrared pump light of 2.7 mJ.

© 2014 Optical Society of America