Half Cycle Terahertz Pulse Generation by Prism-Coupled Cherenkov Phase-Matching Method
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Nonlinear optical terahertz wave generation is a promising method for realizing a practical source with wide frequency range and high peak power. Unfortunately, many nonlinear crystals have a strong absorption in the terahertz frequency region. This limits efficient and widely tunable terahertz wave generation. The Cherenkov phase-matching method is one of the most promising techniques for overcoming these problems. We propose a prism-coupled Cherenkov phase-matching method, in which a prism with a suitable refractive index at terahertz frequencies is coupled to a nonlinear crystal. We demonstrate prism-coupled Cherenkov phase-matching terahertz generation using the DAST and LiNbO3 crystals. With a DAST crystal, we obtain a spectral flat tunability up to 10 THz by difference frequency generation. With a LiNbO3 crystal, we observe a spectral flat broadband terahertz pulse generation up to 5 THz pumped by a femto second fiber laser. The obtained temporal waveform is an ideal half cycle pulse suitable for reflection terahertz tomography.
KeywordsTerahertz wave Nonlinear optics Cherenkov phase-matching Tomography
We thank Norihiko Nishizawa of Nagoya Univ., Masatsugu Yamashita, Katsumi Midorikawa and Chiko Otani of RIKEN, Toshihiko Ouchi of Canon Corp., Jun Takayanagi and Hideyuki Ohtake of Aisin Corp., Hirohisa Uchida of Arkray Corp. for their valuable supports. This work was partly supported by a Grant-in-Aid for Scientific Research (22360026) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
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