Performance of mid-IR high-power ZGP OPO compared in linear and non-planar ring resonators

High average power radiation in the mid-IR spectral region is important for remote sensing, spectroscopy and infrared countermeasures. Frequency conversion in non-linear crystals of zinc germanium phosphide (ZGP) is the main approach to obtain high power sources in the 3–5 μm spectral range [1] . To date, few studies have reported high average power ZGP OPOs, but maintaining a good beam quality remains a challenge [2] , [3] . A particular successful method to suppress higher order resonator modes and improve the beam quality is through non-planar ring cavities RISTRA and FIRE [4] , [5] . In this study, we compare the performance of three OPO cavities at high repetition rate and high average power: linear, RISTRA and FIRE cavities.