High-peak-power long-wave infrared BaGa₄Se₇ optical parametric oscillator with 6.7-13.9 µm widely tunable range

A high-peak-power, widely tunable range long-wave infrared optical parametric oscillator (OPO) based on the BaGa₄Se₇ (BGSe) crystal is demonstrated in this Letter. Pumped by a 1064 nm Nd:YAG laser, a high-peak-power of 0.15 MW was achieved at 9.8 µm with a pulse width of 5.0 ns. At 11.0 µm, a high beam quality of M²x = 4.1 and M²y = 3.3 was achieved. By rotating the BGSe crystal, a broad tuning range of 6.7-13.9 µm was realized. Furthermore, a theoretical analysis was conducted to elucidate the reasons behind the improvement in beam quality in the x-direction as the wavelength of the idler wave increases.