Mechanism of particulate deposition induced by stray light and laser-induced damage of reflectors

Abstract

The laser's optical path system comprises numerous optical components. Reflection and scattering from these components result in constant generation of stray light. Stray light is uncontrollable, and every component in the device faces the risk of irradiation. This irradiation can lead to damage and particulate sputtering on metal surfaces within the device, thereby impacting the performance of downstream components. In this study, we researched the contamination process of high-reflectivity multilayer HfO₂/SiO₂ film components, simulated the process of stray light irradiation on stainless steel components, inducing damage and particulate sputtering through experimentation, and then conducted characterization and damage performance tests on the contaminated samples. When stainless steel is irradiated with low energy density (≥10 mJ/cm²) stray light, it produces non-metallic particulate contaminants that affect the components' damage performance. The higher the laser energy density, the more complex the process of generating particulate contaminants and the more severe the impact on damage performance. Through multi-physics simulation and experimental studies on the damage mechanisms of particulate contaminants, the results indicate that characteristics such as composition and dimension of particulate contaminants play different roles in modulating electric field and temperature during laser irradiation processes. This paper elucidates the sputtering behavior of particulate contaminants due to stray light scattering and reveals the characteristics of irradiation response and damage mechanisms of particulates, which is crucial for studying and understanding the impact of stray light on device performance under load. Studying the impact of stray light on protecting optical components in high-power laser device from contaminants is crucial.