Widely tunable (2.6–10.4 μm) BaGa4Se7 optical parametric oscillator pumped by a Q-switched Nd:YLiF4 laser

https://iopscience.iop.org/article/10.1088/2399-6528/aab007We report on the first BaGa4Se7 nanosecond optical parametric oscillator pumped by Q-switched Nd:YLiF4 laser at 1053 nm. The oscillator exhibits a pump threshold energy as low as 0.25 mJ. Mid-infrared (MIR) idler wave tuning from 2.6 μm to 10.4 μm is demonstrated with an angle-tuned type-I (o-ee) y-cut sample, highlighting the superior performance of this novel large bandgap chalcogenide nonlinear crystal to generate tunable coherent radiation over its full MIR transparency range (0.47–18 μm). The phase-matching data are used to identify the most accurate dispersion relations of this compound among three recently published Sellmeier equations. Damage threshold measurements yielded values as high as 2.04 J cm−2 at 100 Hz pulse repetition rate, one of the largest among existing MIR χ (2)nonlinear materials