Second-harmonic and sum-frequency generation based on birefringence phase matching of BaMgF₄ crystal

BaMgF₄ is a ferroelectric nonlinear crystal with a very wide transparency window ranging from 125 nm to 13µm of the wavelength. Therefore, it is a candidate material to generate ultraviolet or deep ultraviolet laser, which is very important in lithography, semiconductor manufacturing, and advanced instrument development. Here, the second-order birefringence phase-matching processes of the BaMgF₄ crystal were studied, including second-harmonic generation (SHG) and sum-frequency generation (SFG). In the experiments, we measured the phase-matching angle, nonlinear frequency conversion efficiency, and angle bandwidth of SHG and SFG processes of BaMgF₄ crystal, which are in well agreement with the theoretical calculations. This study may promote the research of nonlinear optical process of BaMgF₄ crystal and also the further development of all-solid-state vacuum ultraviolet lasers.