Spectroscopic and fluorescence properties of Sm~(3+)-doped zincfluorophosphate glasses

Optical absorption and fluorescence spectra of Sm³⁺-doped zincfluorophosphate glasses with molar composition of 44P₂O₅+17K₂O+9Al₂O₃+(30–x)ZnF₂+xSm₂O₃ (x=0.01 mol.%, 0.05 mol.%, 0.1 mol.%, 0.5 mol.%, 1.0 mol.%, 2.0 and 3.0 mol.%) referred as PKAZFSm were prepared by melt quenching technique and were characterized through Raman, absorption, emission and decay curve analysis. From the absorption spectra, Judd-Ofelt intensity parameters were determined and were used to predict radiative properties such as transition probabilities (A_R), radiative lifetimes (τ_R), branching ratios (β_R), effective bandwidths (Δλ_eff) and stimulated emission cross-section (σ(λ_p)) for the excited ⁴G_5/2 luminescent level. The decay curve for the ⁴G_5/2 level was single exponential for lower concentration and became non-exponential for higher concentrations. The non-exponential nature of the decay curves of the ⁴G_5/2 level increased with increase in Sm³⁺ ions concentration accompanied by decrease in lifetime due to energy transfer processes among the Sm³⁺ ions. The non-exponential decay curves was well fitted to the generalized Inokuti-Hirayama model for S=6, indicating that the energy transfer among optically active ions was of dipole-dipole interaction. The cross-relaxation mechanism responsible for the quenching of lifetimes and the effect of variation of concentration on the spectroscopic properties were also discussed.