Lead-related centers of UV, visible and near-IR luminescence in SiO2 glass

Absorption, luminescence and luminescence excitation spectra of MCVD-prepared SiO2:Pb glasses with Pb content up to 0.35 wt% were studied. UV and visible luminescence was observed in the 0.3–0.45 and 0.5–0.6 μm ranges. IR luminescence was found in the 0.85–0.95, 1.1–1.2 and 1.3–1.4 μm ranges. Computer modeling of SiO2:Pb glass was performed. The main possible forms of Pb in the SiO2 glass network were found to be threefold coordinated Pb atom, diatomic Pb center, twofold coordinated Pb atom, and possibly fourfold coordinated Pb atom. Structure, electronic properties, absorption and luminescence of the centers corresponding to these forms and of possible lead-related centers responsible for the IR luminescence were calculated. The results of the experiments and modeling suggest that (1) the 0.3–0.45 μm luminescence band is caused mainly by twofold coordinated Pb atoms and partly by threefold coordinated Pb atoms, (2) the 0.5–0.6 μm luminescence band is caused by twofold coordinated Pb atoms, (3) 1.1–1.2 μm IR luminescence band is caused by Pb+ interstitial ions, and (4) 0.85–0.95 and 1.3–1.4 μm IR luminescence bands are caused by complexes formed by interstitial Pb0 atom and a pair of ≡ SiSi ≡ oxygen vacancies.