Multicolor tunable and NIR broadband emission from rare-earth-codoped tantalum germanate glasses and nanostructured glass-ceramics

High photoluminescence efficiency, unusual NIR broadband and tunable emission are possible in erbium-doped and tantalum germanate glasses and nanostructured glass-ceramics. The chemical microenvironment around erbium ions and their influence on optical properties are dependent on the TaO6 clusters formation and tantalum perovskite-like bronze crystallization, which are strongly related to the tantalum oxide content and annealing. Erbium ions are preferably distributed close to tantalum-rich environment, providing an intense emission with minimized nonradiative processes and inhomogeneous broadband NIR emission with increasing site numbers. A more pronounced broadening in the nanocrystalline samples is due to the multi-sites of the tantalum perovskite-like bronze crystalline structure. Green/red tunable emission from up conversion processes was observed since the erbium ions occupy a chemical environment with low phonon energy in the tantalum germanate glass and with close neighbors in the tantalum germanate glass-ceramics. Accordingly, the highly tantalum germanate glasses and glass ceramics are promising for photonic applications in optical amplification, lighting and lasing, as well as for nonlinear optical applications and studies considering the perovskite-like bronze crystalline samples.