Realization of broadband ∼1.8 μm luminescence by level population inversion in Tm3+ doped tellurite glass for laser applications

This study aims to investigate the characteristics of Tm ³⁺ doped TeO ₂–B ₂O ₃–Al ₂O ₃Na ₂O glass. The structures that exist in host glass were obtained from the Raman spectrum. Due to the introduction of sodium and aluminum, the Te O Te bond is broken, and the amount of bridge oxygen is reduced, causing the transformation of [TeO ₄] structural units to [TeO ₃₊₁] and [TeO ₃] structural units. The spectrum characteristics of Tm ³⁺ in the samples were predicted by theoretical calculations. Prepared Tm ³⁺ doped glass has large Ω ₂ and small Ω ₆, which is connected to the ligand field`s asymmetry and the stiffness of the network. Furthermore, under the excitation of 808 nm laser diode, broadband ∼1.8 μm fluorescence was observed and the effective fluorescent bandwidth Δλ _eff of 1830 nm emission in the glass is about 234 nm. For the sample with 0.5 mol% Tm ₂O ₃, the large values of emission cross-section product (9.08 × 10 ⁻²¹ cm ²) and σ _emi × Δλ _eff product (21.25 × 10 ⁻²⁶ cm ³) indicate a good gain property as well as a good gain bandwidth. Eventually, the energy migration process and cross-relaxation process between thulium ions were analyzed. The micro-parameter of the CR process is 4.049 × 10 ⁻⁴⁰ cm ⁶/s. Hence, the results indicate that the prepared Tm ³⁺ doped glass could be a potential candidate for ∼2 μm mid-infrared laser devices.