Accumulation effect of SiO2 protective layer on multi-shot laser-induced damage in high-reflectivity HfO2/SiO2 coatings

Abstract

The accumulation effects in high-reflectivity (HR) HfO2/SiO2 coatings under laser irradiation are investigated. The HR HfO2/SiO2 coatings are prepared by electron beam evaporation at 1064 nm. The laser-induced damage threshold (LIDT) are measured at 1064 nm and at a pulse duration of 12 ns, in 1-on-1 and S-on-1 modes. Multi-shot LIDT is lower than single-shot LIDT. The laser-induced and native defects play an important role in the multi-shot mode. A correlative theory model based on critical conduction band electron density is constructed to elucidate the experimental phenomena. ?2011 Chinese Optics Letters.