Continuous tuning of a narrow-band terahertz wave in periodically poled stoichiometric LiTaO3 crystal with a fan-out grating structure
Nan Ei Yu1, Myoung-Kyu Oh1, Hoonsoo Kang1, Changsoo Jung1, Bok Hyeon Kim1, Kyu-Sup Lee2, Do-Kyeong Ko2, Shunji Takekawa3 and Kenji Kitamura3
Continuous tuning of terahertz waves was demonstrated with seamless change in grating period in a periodically poled stoichiometric lithium tantalite (SLT) crystal. The periodically poled fan-out structure allows wide tunability such as 610 GHz with the bandwidth as narrow as 17 GHz at a carrier frequency of 1.00 THz. Temperature-dependent measurements show a gradual intensity increase of the THz pulses as the temperature decreases. Furthermore, absorption and refractive index of SLT in the THz range were estimated and compared with those of LiNbO3 (LN). The absorption coefficient of the LT crystal at ordinary wave was almost half of that in the LN crystal. SLT could be one of the powerful crystals for high-power THz generation with large optical aperture because of the fewer defects inside the crystal.