High-energy, tunable, long-wave mid-infrared optical parametric oscillator based on BaGa₄Se₇ crystal

A high-energy, tunable, long-wave mid-infrared optical parametric oscillator (OPO) based on the BaGa₄Se₇ crystal was demonstrated in this Letter with 1064 nm laser pumping. The mid-infrared OPO was designed as a double-pass single resonant oscillator (DP-SRO) to reduce the threshold and improve the outputs. Further optimization on the cavity length was theoretically and experimentally studied. With a short cavity length of 30 mm, the output energy of over 1 mJ/pulse at 11 µm was obtained with the pump energy of 39.5 mJ/pulse. In addition, a wide tuning range of 8-14 µm was experimentally achieved by rotating the BaGa₄Se₇ crystal.