Defect formation mechanism dependent on GeO2 concentration in the GeO2 doped quartz glass

In the GeO2 doped SiO2, the formation mechanism of drawing-induced defects and of γ-ray induced defects dependent on the GeO2 concentration were examined. In the 0.4 mol% GeO2 doped SiO2 optical fiber, Ge- and Si-E' center were observed as drawing-induced defects. In the optical fiber with higher GeO2 concentration, however, Si-E' center was not observed. And further, in the 0.4 mol% GeO2 doped SiO2, by annealing treatment, the γ-ray induced GAC shifted to SiE' center. From these results and the structures of defects, in the GeO2 doped SiO2 the migration of unpaired electrons plays an important role in the formation of defects. The mean free path of unpaired electrons in the SiO2 is estimated to be about 1.4 nm from the closet interatomic distance of Ge atoms. (Mori, K.)