Tm3+-doped mixed alkaline-earth zinc-silico-calcium aluminate glasses: A promising material for near-infrared laser

This work is focused on the concentration-dependent study of Tm₂O₃ (0.05, 0.1, 0.25, 0.5, and 0.75 mol%) doped zinc-silico-calcium aluminate glasses for infrared emission. The amorphous nature and good thermal stability (ΔT > 150°C) of prepared glasses are confirmed by X-ray diffraction and differential scanning calorimetry, respectively. The decrease in glass transition temperature and optical band gap, coupled with the increasing trend in optical basicity, linear thermal expansion, molar volume, and oxygen packing density with Tm³⁺ ions concentration, suggests their preference for non-bridging oxygen sites. Two emission peaks at 800 nm (³H₄→³H₆) and 659 nm (¹G₄→³F₄) while another two emission peaks at 1800 nm (³F₄→³H₆) and 1487 nm (³H₄→³F₄) are observed under both 475 and 808 nm excitations, respectively. The realization of emission quenching at 800 nm beyond 0.25 mol% of Tm₂O₃ concentration may be due to resonant energy transfer and cross-relaxation mechanism (³H₄:³H₆→³F₄:³F₄) while for 1800 nm emission, the observed quenching beyond 0.5 mol% of Tm₂O₃ is due to the energy migration to OH⁻ ions and reabsorption (resonant energy absorption). The modified Mc Cumber theory is used to evaluate corresponding emission cross-sections and discussed along with their gain factors for their applicability as 800 and 1800 nm laser materials.