Investigation of emission characteristics in Er³⁺- doped bismuth phosphate glasses for NIR laser materials

Bismuth flourophosphate glasses doped with Er³⁺ ions (0.5 mol %) were synthesized using different modifier fluorides with the aid of melt quenching route. The glass samples were labelled as PBiBaAFT (where AF = Li, Na, Mg, K, Ca and Sr fluorides). The influence of cations of network modifiers on the structure and thereby spectroscopic properties of Er³⁺ ions was analysed via Powder XRD, FTIR, optical absorption and photoluminescence. Existence of relevant vibrational groups and modifications in structure due to the different admixture modifier cations were recognized via FTIR spectra. The Judd-Ofelt parameters abide by the trend Ω₂ > Ω₆ > Ω₄ in the PBiBaLiT, PBiBaKT, PBiBaCaTand PBiBaSrT glasses whereas the trend was noticed to be Ω₂ > Ω₄ > Ω₆ for PBBiNaT and PBiBaMgT glasses respectively. The visible emission spectra were recorded by exciting at 379 nm exhibit three emission bands centered at 526 nm, 544 nm and 686 nm. NIR emission spectra were recorded by exciting at 980 nm exhibit broad emission at 1535 nm. Admixture of different cations could exhibit change in luminescence intensity and radiative parameters of the prepared glasses. Spectroscopic parameters such as radiative transition probability (A), branching ratio (β), absorption cross section (∑), effective bandwidth (Δλ_eff) and optical band gain (σ_e × Δλ_eff) are calculated. The mid infrared spectroscopic features were investigated.