Damage properties of ZnGeP_2 at 2 μm

Damage thresholds at 2 μm exceeding 10 J/cm2 were measured in ZnGeP2 witness samples representing a range of growth runs and surface treatments. Samples grown more recently were more robust, but clear correlations between damage properties and surface quality, coating type, or incident polarization were not observed. Variation in damage threshold both within individual samples and between samples was quite large. Comparison with uncoated diffusion-bonded and single-wafer GaAs shows that uncoated ZnGeP2 damages at slightly lower energy density than does GaAs (approximately 4 J/cm2 versus 5.5 J/cm2, respectively).