Singly-resonant optical parametric oscillation based on the wide band-gap mid-IR nonlinear optical crystal LiGaS2

• First demonstration of optical parametric oscillation with LiGaS2 nonlinear crystal.
• Mid-IR idler pulses generated near 5.46 μm by pumping LiGaS2 at 1064 nm.
• Sub-nanosecond pulses generated with a LiGaS2 optical parametric oscillator.
• Surface optical damage studied in LiGaS2 by nanosecond pulses at 1064 nm.

We demonstrate optical parametric oscillators based on the wide band-gap (3.76 eV) LiGaS2 (LGS), pumped by 100-Hz/8-ns and 1-kHz/1-ns laser sources at 1064 nm. Notwithstanding the modest second order nonlinearity of this material singly resonant operation was possible due to the high optical damage resistivity of LGS. Idler pulses near 5.46 μm were generated with an energy of 134 μJ and duration of 5.4 ns in the first case and energy of 1.1 μJ and sub-nanosecond duration in the second case. We present also optical surface damage measurements at 1064 nm using 14-ns pulses.