[11p-N404-1~9] 4.6 Terahertz Photonics

▲ [11p-N404-2] Terahertz wave generation and detection in GaAs crystals enhanced by using tapered parallel plate waveguides as focusing optics

〇Masahiko Tani¹, Ramon delos Santos², Takashi Furuya¹, Hideaki Kitahara¹, Elmer Estacio³, Joselito Muldera¹, Mary Clare Escano¹, Miezel Talara¹, Michael Bakunov⁴ (1.Univ. of Fukui, 2.Ateneo Univ., 3.Univ. of the Philippines, 4.Univ. of Nizhny Novgorod)

Keywords:terahertz wave, GaAs, tapered parallel plate waveguide

GaAs has excellent potential as a nonlinear optical material for the generation and detection of terahertz (THz) waves with the excitation at the optical communication wavelengths, where cost-effective, compact, and stable femtosecond lasers are available as a pump source. Cherenkov phase-matching angle in GaAs is around 12°, which is substantially smaller than in other representative nonlinear optical crystals. Due to the small Cherenkov angle, a long interaction length of the optical and THz beams is possible in GaAs and no coupling optics is required to couple the generated THz waves to free-space radiation. In this paper, the authors report the results of their research and development of THz emitters and detectors using GaAs as a nonlinear optical medium and tapered parallel plate waveguides (TPPWGs) as a focusing device for THz waves. We present a fully GaAs-based THz-TDS scheme that offers broadband (~3 THz) THz generation and detection and the dynamic range as high as 10⁶. In this scheme, the noncolinear Cherenkov phase-matching is implemented in ~6-10-mm long GaAs crystals. Using TPPWG allows for improving the scheme performance by a factor of ~2-3.