Comparison of femtosecond and nanosecond laser-induced damage in HfO_2 single-layer film and HfO_2-SiO_2 high reflector

HfO2 single layers, 800 nm high-reflective (HR) coating, and 1064 nm HR coating were prepared by electron-beam evaporation. The laser-induced damage thresholds (LIDTs) and damage morphologies of these samples were investigated with single-pulse femtosecond and nanosecond lasers. It is found that the LIDT of the HfO2 single layer is higher than the HfO2-SiO2 HR coating in the femtosecond regime, while the situation is opposite in the nanosecond regime. Different damage mechanisms are applied to study this phenomenon. Damage morphologies of all samples due to different laser irradiations are displayed.