ROLE OF IMPURITIES IN THE 5.16 EV OPTICAL-ABSORPTION BAND OF GE-DOPEDSILICA

The optical absorption band at 5.16 eV and the related photoluminescen ce were investigated in Ge-doped silica samples as a function of the G e content to study the relation between impurities and oxygen deficien t 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 pr ocess. Further, two distinct ranges of Ge-doping were individuated sho wing different dependence of the density of optically active center on the impurity concentration. (C) 1997 Elsevier Science B.V.