Precise frequency shift of NIR luminescence from bismuth-doped Ta2O5–GeO2 glass via composition modulation

Bismuth-doped glasses have received much attention in the last decade due to their broadband near-infrared (NIR) emission. Their optical properties are sensitive to composition and there are a few reports that qualitatively describe the dependence of these properties on their compositions. Yet the actual role of bismuth, as the matrix composition changes, remains fundamentally unclear. In this work, we investigate optical properties of bismuth-doped germanate glasses with different compositions and interpret their dependences in terms of their microscopic structure using Raman and Fourier transform infrared (FTIR) spectra. Beyond qualitative descriptions, quantitative empirical prediction laws are established on the grounds of the relationships between compositions, structures and properties of bismuth-doped germanate glasses. These findings enable precise predictions of the frequency shift of NIR luminescence from bismuth-doped glasses and a better understanding of the nature of bismuth NIR luminescent centers.