Mitigation Procedure for Damage on the Surface of Fused Silica Using a CO2 Laser Beam
X-B. Li, X-D. Yuan, X. Xiang, H-B. Lv, M. Chen, Y. Jiang, S-B. He and W-U. Zheng
The main problems during mitigation for damage on fused silica are presented: air bubbles and ablation. Pre-heating can decrease the number of air bubbles and dilute HF etching gets rid of ablation grains in the nanometre scale. Raster scanning and local mitigation are both feasible for mitigating damage below 10 μm and 10 to 300 μm in diameter. Local irradiation with a high power laser with variable diameter results in the damage threshold of fused silica being effectively improved. Surface appearance and aberration of wave-front are the main problems remaining to be addressed.
Keywords: CO2 laser, fused silica, raster scan, local mitigation, damage threshold