Effects of annealing parameters on transmission wavefront and damage threshold of fused silica

Thermal annealing at high temperature is used to relieve the residual stress of fused silica induced by CO2 laser repair. The effects of annealing environment on surface contamination of fused silica as well as the effects of different annealing temperatures (600 to 900 ℃) and time (3 to 10 h) on residual stress, transmission wavefront, surface roughness, and laser induced damage threshold (LIDT) are investigated. The results show that the residual stress induced by CO2 laser repair can be effectively relieved after annealing at 800 ℃ for 10 h and there is no obvious change in the wavefront and surface roughness of optics. A silica shield box can reduce surface contamination from annealing environment but there are still some contaminations undetectable for X-ray photoelectron spectrosco