An optical member includes a fused silica glass having a concentration of =SiH moiety below detection limit as measured by Raman spectroscopy and a concentration of molecular hydrogen of at least 1x1017 molecules/cm3. The fused silica glass exhibits an induced absorption level which quickly attains an initial peak upon exposure to irradiation and rapidly decays to a low value. The induced absorption level after decaying to the low value remains substantially unchanged by further irradiation.