Luminescence centers in SiO2 and SiO2:GeO2 vad rods sintered under reducing or oxidizing conditions

Photoluminescence (PL) was observed from VAD SiO 2 and SiO 2 :GeO 2 preforms sintered under reducing or oxidizing condition. Three types of diamagnetic luminescence centers, Si-E′ and Ge-E′ center were found in glass samples. Intensity of the luminescence was strongly dependent on sintering atmosphere; reducing atmosphere accelerated the PL. The observations suggest that reduced Si or Ge species, Si(III), Si(II), Ge(III) and Ge(II), are responsible for the PL.