Optical AR Coatings of the Mid-IR Band for ZnGeP2 Single Crystals Based on ZnS and Oxide Aluminum

In this work, the parameters of antireflection interference coatings based on alternating layers ZnS/Al2O3 laser-induced damage threshold (LIDT) ZGP crystals under action Ho:YAG laser radiation at a wavelength 2.097 μm were determined. The coating deposition was carried out using ion-beam sputtering method. LIDT sample with ZnS and Al2O3 equal to WoE = 3.45 J/cm2, uncoated 2.23 J/cm2. An increase in optical breakdown by ~55% observed after an AR materials. assumption made about absence local fluctuations composition mechanical stresses case coated sample, namely that leads good adhesion multilayer polished surface crystal, as result compared due closure dangling chemical bonds bulk defects emerging surface.