Laser strength mirrors for high-power NIR-region solid-state lasers

Some aspects of obtaining high reflective (KR) dielectric mirrors with high damage threshold (LDT) for high-power solid-state near infrared region (NIR) lasers are considered. Optical properties of these mirrors were investigated as properties of each alternate layer evaporated with high-index (H) or low-index (L) materials as multilayer system that depends on mirror construction, parameters of evaporation, ion-beam influence, substrate materials and quality of substrate surface. Refractory oxides ZrO2, HfO2, Ta2O5, Al2O3 and SiO2 were used as stat ting materials for evaporation. Ion-beam influence was estimated as changing of optical absorptance at a wavelength 1.064 mu m by laser modulated photo-thermal radiometry (LMPTR). Besides the quality of various work-up substrate surface was controled By this method also. It was noticed that substrates with different surface roughness (sigma, rms) had different absorption. It was notice that band edge of absorption of pure substratesd in UV region influenced on laser damage threshold (LDT) of mirrors. Optical properties of evaporated mirrors were tested as the ability of strength for laser irradiation as cavity-mirrors of higth power lasers. ZrO2/SiO2 mirrors had the most high laser strength. Estimated value of laser density was 3.6 GW/cm(2).