High Power and Efficient 4.43 μm BaGa₄Se₇ Optical Parametric Oscillator Pumped at 1064 nm

A high power and efficiency mid-infrared optical parametric oscillator based on a BaGa4Se7 crystal is demonstrated in this paper. It was pumped by a 500 Hz Q-switched Nd:YAG laser at room temperature. Without cooling, up to 0.76 W output power at 4.43 μm was generated with respect to the incident pump power (1064 nm) of 5.52 W, corresponding to an optical-to-optical conversion efficiency of 13.7%. The corresponding slope efficiency was as high as 18.7%. The pulse width of the signal wave was 5.2 ns at the pump pulse of 13.7 ns. To the best of our knowledge, this is to date the highest output power achieved at 4–5 μm from a 1064 nm pumped BGSe OPO laser. Considering that no additional cooling system was applied, this work provides a good solution for a high-efficient, compact or even portable mid-infrared solid-state laser device.