The impact of Yb3+ ions concentration on the structure and NIR luminescence of Er3+ doped niobium based phosphate glasses

This study investigates the influence of Yb³⁺ ion concentration on the physical and luminescence properties of Er³⁺-doped niobate-based phosphate glasses. A system of novel glasses with chemical composition of P₂O₅: Nb₂O₅: Na₂O: Li₂O: Er₂O₃: Yb₂O₃ were synthesized through melt quenching technique. The density of the samples shows an increasing trend while the molar volume demonstration a decreasing trend with increasing Yb₂O₃ concentration. The Judd-Ofelt (JO) theory was utilized to compute the JO intensity parameters, which subsequently yielded the radiative lifetimes of Er³⁺ ions, fluorescence branching ratios, and radiative transitions probability. These parameters exhibit a trend of Ω₂ > Ω₄ > Ω₆. Furthermore, the optical band gap (E_opt) was found to decrease with Yb₂O₃ doping, which was attributed to the formation of non-bridging oxygen (NBOs) in the glass network. The increase in NBOs reduced the separation between the valence-band maxima and conduction-band minima, leading to a more favorable environment for energy transfer processes. Additionally, owing to the energy-transfer among Yb³⁺ and Er³⁺ ions, the intensity of peak at 1530 nm corresponding to the near-IR luminescence band (⁴I_13/2 → ⁴I_15/2) changes with Yb₂O₃ concentration. The optimum molar ratio Er³⁺: Yb³⁺ i.e. 1:0.7, show the highest luminescent ratio for these glasses. This enhancement in luminescence is attributed to the effective energy transfer mechanism between Yb³⁺ and Er³⁺ ions, making these glasses highly suitable for applications in photonic devices, such as optical amplifiers and lasers. The findings of this study provide valuable insights into the design and optimization of rare-earth-doped phosphate glasses for laser and other advanced optical applications.