Study of convexity on nanosecond laser-induced damage growth in fused silica

Abstract

Damage growth in fused silica under ultraviolet nanosecond laser irradiation poses a significant threat to the stable operation of high-power laser systems and shortens the service life of optical components. In this study, an experimental scheme was developed in which initial damage sites were deliberately fabricated and subsequently subjected to medium-aperture laser irradiation to induce further growth. A time-resolved shadowgraph imaging system was designed to capture the dynamic evolution of damage morphology and polarization characteristics. Statistical analysis of the final damage images—acquired from both transmission-view and side-view microscopic imaging systems—revealed that the damage morphology, particularly the structure of radial cracks, plays a key role in determining the damage growth coefficient. To quantitatively characterize the morphology of radial cracks, a novel morphological parameter, convexity, was introduced. The analysis showed that damage sites with lower convexity generally exhibited higher growth coefficients and shallower damage depths. These findings provide valuable theoretical insights for the prediction and mitigation of laser-induced damage and establish a foundation for the further refinement of damage growth models.