Published online by Cambridge University Press: 25 February 2011
Photo-luminescence(PL) in VAD silica preforms sintered under reducing or oxidizing condition was observed. Two types of diamagnetic luminescence centers and the Si-E′ center were found in pure silica glass. The intensity of photoluminescence was strongly dependent on the sintering atmosphere. This observation suggests that reduced Si species, Si(III) and Si(II), are responsible for the luminescence.