Influence of the synthesis atmosphere on NIR fluorescence behavior of Ce/Er co-doped bismuth glass through valence state changes of cerium

This work investigates the near-infrared emission characteristics and energy transfer between erbium and cerium in bismuth glass by the reaction atmosphere process. The Er3+:1.5μm emission can be successfully enhanced by performing a reduction conversion of Ce4+→Ce3+ using a reducing atmosphere. The discrepancies of the energy structure between Ce3+ and Ce4+ result in a contrasting sensitizing effect on Er3+:1.5μm emission intensity and decay lifetime. The results show that a significant amount of Ce3+ is present in glasses prepared in a reducing atmosphere, whereas Ce4+ is the main species in an oxidizing atmosphere by means of absorption spectra and XPS curves. The reason for upconversion quenching is also discussed.