Laser-induced damage of multilayer high-reflectance coatings for 248 nm

Abstract

In order to study the effect of material properties on the laser induced damage of dielectric coatings at a wavelength of 248 nm, multilayer coatings were deposited by electron beam reactive evaporation technique onto fused silica substrates with the materials of hafnium oxide, aluminum oxide and silicon dioxide. Laser-induced damage thresholds (LIDTs), morphologies and profiles of damage sites of multilayer thin films were measured to investigate the damage mechanism. Besides, with our programmed software, the temperature rise in the multilayers was calculated to better understand the relationship between damage morphology, electric field peak location and depth of damage sites. The results indicate that the absorption of defect and the electric field distribution of thin film greatly contribute to LIDTs of thin films, and the control of defect, especially defect with strong absorption, is still the only way to improve the laser radiation resistivity of coatings in the UV spectral region.