Damage Mechanisms and Characteristics of the Cavity Reflectors Damage Mechanisms and Characteristics of the Cavity Reflectors

Abstract

For high-power outputs from rare-gas excimer lasers, cavity reflectors having high reflectivity and free from radiation damage areprimarily required. We measure reflectivities and surface topographic features for some reflectors made of Alfilms deposited on SiO₂ substrates, SiC films deposited on graphite substrates, SiO₂ glasses, and single crystals of W, Mo, Si and Cr. The results of surface damageobserved on Al and Si mirrors as well as a thermodynamical calculation show that the surface damage is caused mainly by surfacemelting due to strong absorption of laser energy.