Degradation mechanism of laser-induced damage of porous ZrO2/SiO2 high reflective films in vacuum

Abstract

Degradation mechanism of laser-induced damage of porous ZrO2/SiO2 high reflective films was discussed in vacuum. The experimental results show that the laser-induced damage (LIDT) in vacuum dropped to 57% of its atmospheric value and 65% of the value filled with air after vacuum pumping for the high reflective films. Typical damage micrographs of the films in air and in vacuum were obtained, showing the distinct damage morphologies. Such a degradation mechanism of laser-induced damage was found to originate from the water desorption on the surface and internally in porous films, which could cause a decrease of the thermal conductivity. A theoretical and kinetic model was used to illustrate the occurrence of the damage and corresponding damage morphologies.