ErF3-doped TeO2-Ga2O3-BaF2-AlF3-Y2O3 (TGBAY) glasses with high fluorescence efficiency and a high thermal damage threshold were developed for potential mid-infrared fiber laser applications. A model 2.7-μm fiber laser based on this material was analyzed using rate and propagation equations. Under 808 and 980 nm laser pumping, fluorescence emissions with central wavelength at 1.55 and 2.73 μm were detected. Based on the Judd-Ofelt (J-O) theory, the intensity parameters (Ωλ, λ = 2, 4, and 6) and radiative transition property were calculated and characterized through absorption and emission spectra. The results indicated that tellurite-gallium oxyfluoride glass had a high glass transition temperature (Tg, ∼391 °C), large emission cross sections at 1.55 μm (6.32 × 10−21 cm2) and 2.73 μm (9.68 × 10−21 cm2) as well as a longer fluorescence lifetime (6.84 ms at 1.55 μm and 262 μs at 2.73 μm) relative to the conventional Er3+-doped tellurite glass. The temperature dependence of the emission spectra indicated that TGBAY-2Er glass was more favorable to achieve infrared emission at low temperatures. Numerical simulation revealed the feasibility of achieving a ∼2.7 μm fiber laser operation based on the developed Er3+-doped tellurite-gallium oxyfluoride glass fiber. © 2021 Author(s).