Damage characteristics of fused silica under partially coherent beams

The damage characteristics of fused silica irradiated by partially coherent nanosecond laser beams with tunable spatial coherence were systematically investigated. The laser-induced damage threshold (LIDT) was found to increase as the spatial coherence decreases. This improvement in LIDT is attributed to the suppression of speckle-induced local intensity enhancement and effective nonlinear self-focusing in fused silica. The underlying damage mechanisms were further analyzed by combining damage morphology with z-scan measurements. Our results demonstrate that partially coherent beams with low spatial coherence can mitigate local intensity enhancement and suppress self-focusing, thereby improving the damage resistance of fused silica. These findings are of practical significance for the design and optimization of high-power laser systems.