Rise and Decay of 3.15 eV Luminescence in Germanosilicate Glass: Influence of Glass Densification

A wide variety of defects in germanosilicate glass observed in absorption and in luminescence spectra results in the energy transfer from some defects to others. Such a process was directly demonstrated by Gallagher and Osterberg1 and Bagratashvili et al.2 when 3.15 eV luminescence of germanium oxygen-deficient center (GODC) was excited by 5 eV photons. Along with usually observed decay of luminescence with about 100 µs lifetime they observed an initial rise of the luminescence with time of about 10 µs. To explain this phenomenon, Gallagher and Osterberg added to the commonly accepted scheme of GODC’s states (S0, S1 and T1) one more energy state of another defect. This state can nonradiatively transfer its excitation to the triplet state of GODC and this results in the rise of triplet-to-singlet luminescence. In this case the rate of the rise is governed by the lifetime of additional state.