Small size damage mitigation on fused silica surface with CO2 laser

CO2 laser with 10.6 μm wavelength is used to irradiate damage of different types. Testing with 351 nm wavelength ultra-violet laser, it is found that for damage pits with size below 80 μm and scratchs with size below 40 μm, the larger damage size is, the less threshold enhancement of damage is. Mitigation is not distinct when the size of scratch is wider than 40 μm. During laser conditioning, heat stress results from short interaction time and asymmetrical temperature distribution, thus radial crack appears after damage and could expand if exposed to ultraviolet laser. After annealed in an oven for 3 hours, crack would not occur on the sample with damage.