Abstract

Nonlinear optical (NLO) crystals are in common use to generate Terahertz (THz) waves. NLO crystals, such as 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST), LiNbO₃, LiTaO₃, and GaAs, are used as effective THz sources based on their second-order nonlinearity. Various studies have been carried out on THz generation from NLO crystals using parametric processes, difference frequency generation, optical rectification, and coherent phonon emission. Effective THz generation, however, is suppressed by the high absorption coefficient of the NLO crystals. Because the refractive index of NLO crystals is different for optical and THz frequencies, the phase-matching conditions and the coherent length for optical rectification are issues for effective THz generation.

© 2015 Japan Society of Applied Physics, Optical Society of America