Optimization on the frequency conversion of LiGaS2 crystal

Abstract

Based on newly improved optical parameters of the excellent biaxial crystal LiGaS 2 , its phasematching upon second harmonic generation and general parametric processes are investigated. In particular, the issue of optimal phase-matching is solved by a computation on figureof-merit (FM). It is found that the effective fundamental wavelength of second harmonic generation entirely covers the 3-5 µm atmosphere window and mid-IR signals of 2-12 µm can be generated by suitable parametric processes. Analysis of the FM and dispersion verifies a quite effective type II parametric process: from a pump in the range of 0.8-1.0 µm to an ultrashort pulse generation at 6-12 µm and also suggests a type I pump at 1.7-1.9 µm for 3-5 µm pulse generation. The computation definitely renders an optimal phase-matching in the XY principal plane for type II configuration, or in a special direction for type I case, far away from the commonly used XZ principal plane.

Temperature-Dependent Optical Properties of Bismuth Triborate Crystal in the Terahertz Range: Simulation of Terahertz Generation by Collinear Three-Wave Mixing in the Main Crystal Planes

“…The efficiency of DFG depends not only on the corresponding nonlinear susceptibilities but also on the number of properties of a nonlinear crystal, such as the laser damage threshold, absorption coefficients, birefringence, and group-velocity mismatch in different spectral ranges, PM conditions, and geometric dimensions. All these properties depend in a complex way on the pump radiation parameters, including the pump wavelength, pulse duration, beam spatial parameters, and initial pump beam intensity [14,15]. For example, in an LBO crystal that does not possess high nonlinear susceptibility, a record, up to 90%, energy efficiency of second-harmonic generation (SHG) was achieved at a pump intensity of 775 MW/cm 2 [16].…”