A Comparative Study of BaGa4S7, BaGa2GeS6, and Ba2Ga8GeS16 Nonlinear Crystals for Optical Parametric Oscillators Pumped at 1 or 2 μm

The optical properties of the nonlinear crystals BaGa4S7, BaGa2GeS6​ and Ba2Ga8GeS16 were examined. The study covers transparency and tuning range for pumps at 1.064, 1.5, 1.85 and 2.09 μm, as well as the laser-induced damage threshold (LIDT) measured at ~2 μm with a 1 kHz repetition rate using the R-on-1 method. The study has demonstrated that the crystals exhibit a high LIDT of around 5.8–6.4 J/cm2. The combination of a high damage threshold and a broad transparency range of up to 12 μm suggests that sulfur-containing barium chalcogenide crystals hold promise for the development of widely tunable high-energy pulsed radiation sources for various applications, such as medical laser surgery and ablation.