Ni-doped fluorosulfates with broad NIR luminescence

Glasses containing multiple anions hold promise as a novel class of laser gain media, for nonlinear optical applications, or for encapsulating crystalline phases, e.g., in solid state lighting. In particular, the broadly tunable interionic competition between the varying anion species enables a wide variety of physical properties, ligand arrangements and, most notably, high flexibility in the design of crystal precipitation routes. Here, we report on Ni²⁺-doped fluorosulfate (FS) glasses in which devitrification leads to strong and broadband near-infrared luminescence from embedded crystalline sulfates and alumina. Luminescence occurs at ∼1300 nm with a full width at half maximum of ∼285 nm, resulting from the ³T₂(F) → ³A₂(F) transition of Ni²⁺ in octahedral coordination. This demonstrates the suitability of low-melting mixed-anion glasses for exploiting the luminescence behavior of sulfate species.