Behavior analysis and threshold prediction of laser-induced damage in fused silica based on 2-D thermal diffusion model

Abstract

Laser-induced damage is a bottleneck problem that restricts the development of high-power laser facilities. According to the theory of carriers contributed thermal conductivity, we established a 2-D thermal diffusion model for fused silica. This model provides a detailed description of the dynamic evolution of the temperature field distribution during laser pulse loading. The heat deposition core, which consists of the defect and the high-temperature fused silica, continuously absorbs the laser energy. This results in forming a solid absorption wavefront that diffuses in the anti-laser transmission direction. The results of the numerical simulation and the experimental results show that the evolution law of the heat deposition core in the energy deposition process is directly related to the final damage state. According to the evolution characteristics of the instantaneous peak temperature and its position of the heat deposition core, we calculated the critical parameter αth, whose amplitude indicates the maximum absorption capacity of the defects that optical elements can carry. Further numerical simulations established the mathematical correlation of the αth with the laser pulse waveform. The results of the study provide an important theoretical basis for predicting and evaluating the laser-induced damage of optical elements under high-power laser radiation.