Al2O3 modification of TeO2-ZnO-Na2O glasses: Tailored network structure for enhanced thermal stability and 2–3 μm mid-infrared emission

Tellurite glasses with the composition 67TeO 2 -3Al 2 O 3 -xZnO-(30-x)Na 2 O (x = 0–20 mol%) were synthesized via melt-quenching. Raman analysis revealed Al/Zn synergistically strengthened the network via Al-O-Te/Zn-O-Te bonds below 15 mol% ZnO, whereas excess ZnO triggered Zn 2+ /Al 3+ site competition, reducing crystallization resistance.   The glass with 15 mol% ZnO (TANZ) shows optimal thermal stability ( T g  = 311 °C, ΔT = 139 °C) and serves as the host for obtaining mid-infrared emission. The Ho 3+ /Yb 3+ co-doped TANZ glass shows high absorption and emission cross-sections of 7.36 × 10 –21 cm 2 and 5.86 × 10 –21 cm 2 , respectively, along with a long lifetime of 1.33 ms at 2 μm. These results highlight the potential of TANZ glasses as robust gain materials for mid-infrared fiber lasers.