Effects of Vacuum on Fused Silica UV Damage

Damage points induced by 355nm laser irradiation increase more quickly on the surface of fused silica in vacuum of about 10^-3Pa than in atmospheric air at the same fluence. The larger concentration of point defects in vacuum is confirmed by photoluminescence intensity. X-ray photoelectron spectroscopy and infrared absorption indicate the formation of sub-stoichiometric silica on the surface. The degradation mechanism of fused silica in vacuum is discussed.