Optimized 2 μm high-gain luminescence properties in Ho3+ and Yb3+/Ho3+ doped TeO₂-WO₃-GdF₃ glass by alkali and alkaline earth metal

Abstract

The 2 μm laser gain materials are currently a focal point in optical glass research, often facing challenges such as low gain and small absorption/emission cross-sections. Building on previous research, this work investigates a novel TeO₂-WO₃-GdF₃-K₂O-BaO (TWGKB) glass doped with Ho³⁺ and Yb³⁺/Ho³⁺. By enhancing the optical basicity through the addition of alkali metal (K₂O) and alkaline earth metal (BaO), the Stokes shift between the emission and absorption peaks was increased, leading to 13% enhancement in luminescence intensity and the maximum FWHM reached 175.95 nm at 2 μm band. The sufficiently large absorption (1.49×10⁻²⁰ cm²) and emission cross-section (3.20×10⁻²⁰ cm²) demonstrate that energy from the pumping source can be effectively utilized, achieving the maximum gain coefficient of 6.00 cm⁻¹ at 2.05 μm. The Ho³⁺ ions in the TWGKB glass system have lower coordination field symmetry and high quality factor (χ). The pumping band is optimized to commercial wavelength with Yb³⁺ doping and maintains an efficient forward energy transfer from Yb³⁺ to Ho³⁺. Compared with the other glass systems, the excellent optical properties indicate that the TWGKB has ideal development potential at 2 μm band.