Abstract: 3-5 μm mid-infrared laser has broad applications in atmospheric communication, environmental monitoring, medical treatment, and defense. In this study, a series of glasses with compositions of 70TeO₂-25ZnO-5La₂O₃, doped with Dy³⁺, Yb³⁺, and co-doped with Dy³⁺/Yb³⁺, were prepared using the melt-quenching method in an atmosphere-protected glovebox. The thermal, structural properties, hydroxyl content, and mid-infrared luminescence performance of the glasses were characterized through measurements such as differential scanning calorimetry, X-ray diffraction, Raman spectra, transmission spectra, and 3 μm band fluorescence spectra. The results indicate that the 70TeO₂-25ZnO-5La₂O₃ glass possesses high resistance to crystallization (ΔT=101 ℃) and low phonon energy (~760 cm^-1). Under 980 nm LD excitation, Dy³⁺/Yb³⁺ co-doped tellurite glass produces a broadband fluorescence emission around the 3 μm region, with a full width at half maximum (FWHM) of 326 nm. This is attributed to the high energy transfer efficiency from Yb³⁺ to Dy³⁺ (98.74%) and the low hydroxyl absorption coefficient near 3 μm (~0.32 cm^-1). Based on Judd-Ofelt and Dexter theories, the radiative transition probability, fluorescence branching ratio, and other spectroscopic parameters of Dy³⁺ ions, as well as the microscopic parameters of Yb³⁺→Dy³⁺ energy transfer, were calculated. The primary energy transfer pathways were discussed and identified as Yb³⁺: ²F_5/2→Dy³⁺: ⁶H_7/2, ⁶F_9/2. The study shows that the low-hydroxyl Dy³⁺/Yb³⁺ co-doped TeO₂-ZnO-La₂O₃ glass can serve as an excellent 3 μm mid-infrared gain medium.

Key words: mid-infrared, Dy³⁺/Yb³⁺ co-doped, Judd-Ofelt theory, Dexter theory, energy transfer microparameter