Role of impurities in the 5.16 eV optical absorption band of Ge-doped silica

The optical absorption band at 5.16 eV and the related photoluminescence were investigated in Ge-doped silica samples as a function of the Ge content to study the relation between impurities and oxygen deficient defects. The data, collected in a wide doping range, showed that the dependence of the intensity of the 5.16 eV absorption band on the Ge content depends on the thermochemical parameters of the preparation process. Further, two distinct ranges of Ge-doping were individuated showing different dependence of the density of optically active center on the impurity concentration. © 1997 Elsevier Science B.V.