Comparative studies of laser-induced damage of several single-layer optical films

Single-layer optical films, ZrO2, SiO2 and HfO2, were deposited on K9 glass substrates by ion beam sputtering deposit technique in order to study laser-induced damage threshold (LIDT) and damage mechanism. Impurities and defects will result in strong weak absorption coefficient and photothermal signal. Further LIDT is inverse proportional to the absorption coefficient of the films. AFM images of as-deposited films showed a similar roughness of 2-4 nm. Among the films, ZrO2 film has a pore structure, which results in the largest weak absorption, photothermal effect and smallest LIDT. HfO2 film has the largest LIDT (22.13 J/cm2) due to the smallest number and size of both defects and impurities on the surface. Different films have different damage morphology, which is related to the morphology of defects or impurities in the film before laser irradiation and the interface between films and substrates. In order to enhance LIDT, it is important to prepare high-quality film and passivate the defects in the films