Theoretical study of tunable terahertz wave based on difference-frequency generation in AgGaSe2 crystal

Based on the technology of the collinear phase-matching about three-wave interactions in uniaxial crystal, the phase-match angle, walk-off angle, acceptance angle and effective nonlinear coefficient of the terahertz wave based on difference-frequency generation are calculated under oeo type and oee type phase-matching conditions in AgGaSe2 crystal pumped by CO2 laser. The results show that terahertz wave tunable range is very wide with two types of phase-matching conditions, and the walk-off angles are less than 1°, the acceptance angles are large enough. In the vast majority of terahertz wave region, effective nonlinear coefficient of oee type is much larger than that of oeo type, thus oee type is more suitable to be used in experiments.