Physical mechanism of pulsed laser interaction with fused silica optics during CO₂ laser mitigation process

The intrinsic physical mechanism of CO₂ laser rapid ablation mitigation micro-defects on fused silica optics surface are studied through experiments and simulations. Based on the multi-physics coupling mathematical model involving the stages of phase transition, melting flow and evaporative ablation, the calculated depth of Gaussian ablation crater and protrusion height at the edge formed by single laser pulse are 5.05 μm and 25 nm respectively, which agrees well with the experiment. Then, the temperature distribution, heat affected zone, solid-liquid transition process and surface morphology evolution under the action of moving pulsed laser are analyzed. Through studies of the relationship between laser parameters and processed surface quality, it can be concluded that the periodic structural features at the bottom of surface morphology are formed by the superposition of residual height of linear laser processing. Laser with short pulse width is more likely to cause material redeposition on the surface of fused silica optics.