Mitigating laser induced damage in fused silica with CO₂ laser

Laser induced damage sites in fused silica were irradiated by a galvanometer scanned CO2 laser. Most damage sites are completely repaired (no ablation deposits, air bubbles and cracks) and the largest is 500 m in diameter. Compared with localized mitigation, scanning mitigation can repair larger-sized damage, and bring about smaller surface deformation and lower thermal stress. The damage testing at 355 nm shows that, 80% of the mitigated damage sites can withstand the laser power density up to the initial damage threshold of the substrate.