Tunable broadband photoluminescence from bismuth-doped calcium aluminum germanate glasses prepared in oxidizing atmosphere

Tunable photoluminescence (PL) from transparent inorganic glass matrices is of interest for applications demanding a semitransparent photoconverter that does not elastically scatter incoming light. For this purpose, bismuth (Bi)-doped optical materials exhibit unique spectral characteristics in terms of bandwidth and emission tunability. Here, we demonstrate a facile route for preparing such converters from Bi-doped calcium-aluminate and calcium-aluminogermanate glasses. These glasses offer tunable PL across the near violet and visible-to-near-infrared (NIR) spectral range, with an emission lifetime in the range of 300 μs. The addition of GeO₂ exerts a decrease in optical basicity, which in turn enables the stabilization of NIR-active low-valence Bi species for broadband NIR PL.