Effect of γ-ray irradiation on the optical property and laser damage performance of silica

High purity fused silica samples have been irradiated by 60Co γ-ray at the doses of 50, 500 and 5000 kGy, and the effect of γ-ray irradiation on the optical property and laser damage performance of silica have been investigated. After γ-ray irradiation, there is no obvious change on the surface of silica observed. However, the surface roughness increases slightly with increasing γ-ray irradiation dose. When the irradiation dose reached 500 kGy and above, a broad absorption band at 215 nm, ascribed to E′ color center, is significantly observed and its intensity increases greatly with increasing dose. After laser irradiation, the distribution of laser induced damage threshold (LIDT) is related to γ-ray dose, and the LIDT decreases monotonously with increasing dose. A mechanism for the degradation of laser damage resistance is presented.