Optical properties of Er3+ and Yb3+/Er3+-doped NaF-Na2SO4-Al(PO3)3 fluoro-sulfo-phosphate glasses

Fluoro-sulfo-phosphate (FPS) glass is of current interest as potential material for laser application due to its good glass-forming ability, thermal, and chemical stability as well as the complicated local environment for incorporated species. Herein, the physical and luminescent properties of Er³⁺ and Yb³⁺/Er³⁺-doped FPS glasses vs S/F ratio are investigated comprehensively. The low melting temperature (750°C) leads to fewer ingredients evaporation and easier operation. The sulfate addition depolymerizes the structure of FPS glasses, leading to either monotonic or nonmonotonic variations of physical properties, while no deterioration in thermal and limited one in chemical stability is caused. The addition of sulfate also modifies the local structure around optical active species and thus, leading to higher emission cross section (1.52 × 10⁻²⁰ cm²), effective linewidth (68.4 nm), figure of merit (5.61 × 10⁻²³ s cm²), gain bandwidth (102.44 × 10⁻²⁷ cm³), and energy-transfer microparameters (51.87 × 10⁻³⁹ cm⁶/s), implying high possibility to serve as 1.5 μm laser application.