Thermal and mechanical damage characteristics of two reflective multilayer films under laser irradiation

Based on the standing-wave theory, a theoretical model with high energy absorption at the surface and interfaces is employed to describe laser-induced damages to optical multilayer films. The temperature distributions in two types of reflective multilayer films are calculated, and the characteristics, modes and damage thresholds are analyzed. The results show that energy absorption is mainly determined by the distribution of the standing-wave and extinction coefficients of the material. Multi-peaks over the temperature profiles are found at the surface and interfaces, where the optical multilayer films are prone to damage. Melting and falling off are two main kinds of damage mode, while inclusion, if present, may cause spallation of the layers.