Equivalent explosion simulation model for studying the laser-induced damage process of KDP crystal

Abstract

When Potassium Dihydrogen Phosphate (KDP) crystal is irradiated by nanosecond laser with fluences exceeding its damage threshold, laser-induced damage occurs in the bulk or on the surfaces of crystal components. Such damage process is a multi-physical coupling process which is composed of energy deposition stage, temperature/pressure rising stage and subsequent micro explosion stage. So far, great efforts have been made in modeling the energy deposition and temperature/pressure rising stages of the damage process, but little attention has been paid on the subsequent micro explosion event. As a result, it is still impossible to reproduce the laser damage phenomena such as damage crater formation and shockwave propagation with the existing damage models. To address this concern, equivalent explosion simulation model for studying the laser-induced damage process of KDP crystals has been constructed by finite element method (FEM). According to the model, explosion energy leading to damage, formation of damage craters and propagation of shockwave can be obtained. Moreover, laser damage experiments combined with time-resolved techniques have been utilized to investigate the impact of laser fluences on the shockwave speed. Experiment results agree well with the simulated phenomenon, which has proved the validity of the simulation model.