Theoretical and experimental investigations of angular effects in pulsed CO₂ laser ablation with fused silica

Laser ablation is widely recognized as a non-contact and contamination-free processing technology for fabricating fused silica optics. However, when machining curved optics, the introduction of incidence and path angles inevitably alters laser beam characteristics and complicates path planning. Due to the complex coupling interactions and unique properties of fused silica, the unclear influence mechanism of these angles on laser ablation has become a bottleneck hindering further advancements. In this study, a three-dimensional multi-physics model was developed to elucidate the underlying influence mechanism. Through comprehensive theoretical simulations, the effects of different incidence and path angles on surface morphology, temperature field, heat-affected zone (HAZ), and thermal stress were systematically investigated. The results demonstrate that the incidence angle modulates ablation quality and thermo-mechanical properties by reducing power density, inducing spot distortion, and lowering material reflectivity. Meanwhile, the path angle influences machining morphology, temperature and HAZ distribution by altering the direction of spot distortion. Additionally, experimental measurements validated the simulation results, demonstrating an average error of 4.81% in ablation depth across incidence angles from 0° to 20°. This work not only deepens the understanding of the laser ablation process but also provides a theoretical foundation for achieving high-quality fabrication of curved fused silica optics.