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 Tm3+ doped TeO2–B2O3–Al2O3Na2O glass. The structures that exist in host glass were obtained from the Raman spectrum. Due to the introduction of sodium and aluminum, the TeOTe bond is broken, and the amount of bridge oxygen is reduced, causing the transformation of [TeO4] structural units to [TeO3+1] and [TeO3] structural units. The spectrum characteristics of Tm3+ in the samples were predicted by theoretical calculations. Prepared Tm3+ doped glass has large Ω2 and small Ω6, 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 Δλeff of 1830 nm emission in the glass is about 234 nm. For the sample with 0.5 mol% Tm2O3, the large values of emission cross-section product (9.08 × 10−21 cm2) and σemi × Δλeff product (21.25 × 10−26 cm3) 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 cm6/s. Hence, the results indicate that the prepared Tm3+ doped glass could be a potential candidate for ∼2 μm mid-infrared laser devices.