Intense 2.71-μm fluorescence emission in low hydroxyl heavily Er3+-doped fluorotellurite glass for mid-infrared fiber laser

Heavily Er ³⁺-doped TeO ₂–BaF ₂–La ₂O ₃–LaF ₃ (TBLL) glasses with low hydroxyl absorption ( α _OH− ≈ 0.025 cm ⁻¹) and high glass transition temperatures ( T_g > 437 °C) were prepared. The Raman spectra and differential scanning calorimetry (DSC) curves were measured to characterize the structural and thermal properties of the glass samples. The emission properties of Er ³⁺-doped TBLL glasses were studied under a 980 nm LD excitation, and the related transition mechanism was discussed. Intense fluorescence emission was noted at 1.55 μm and 2.71 μm, and the intensities of emissions increased monotonically as the Er ₂O ₃ doping concentration increased from 0.5 to 6.0 mol%. The absorption and emission cross sections of Er ³⁺-doped TBLL glass at 2.71 μm were estimated to be 7.90 × 10 ⁻²¹ and 8.47 × 10 ⁻²¹ cm ² using the Fuchtbauer–Ladenburg theory, respectively, which are much higher than those of many reported tellurite glasses. Furthermore, the undoped and 6.0 mol% Er ₂O ₃ doped TBLL bare fibers were prepared. Their chemical durability was tested in deionized water, and the results indicated that the TBLL glass exhibited good antideliquescence ability. Finally, a broad emission band at ∼2720 nm was detected in the 6.0 mol% Er ₂O ₃ doped TBLL bare fiber. These results demonstrate that the novel Er ³⁺-doped TBLL fluorotellurite glass is a candidate for ∼3 μm fiber lasers.