Photoluminescence and energy transfer studies of Dy3+-doped fluorophosphate glasses

Dy3+-doped fluorophosphate glasses with composition (in mol%) (56 − x/2)P2O5 + 17K2O + (15 − x/2)BaO + 8Al2O3 + 4AlF3 + xDy2O3, x = 0.01, 0.05, 0.1, 1.0 and 2.0, have been prepared by melt quenching technique. The luminescence spectra and lifetimes of 4F9/2 level of Dy3+ ions in these glasses have been measured using the 457.9 nm line of argon ion laser as an excitation source. The free-ion calculation and Judd–Ofelt analysis have been performed. The room temperature emission spectra corresponding to 4F9/2 → 6HJ (J = 7/2, 9/2, 11/2, 13/2 and 15/2) transitions of Dy3+ ions were measured. The fluorescence decay from 4F9/2 level have been measured by monitoring the intense 4F9/2 → 6H13/2 transition. The lifetime of the decay is obtained by taking the first e-folding times of the decay curves and is found to decrease with increase in Dy3+ ions concentration due to concentration quenching. The decay curves are found to be perfectly single exponential for samples with low Dy3+ ion concentration. The non-exponential decay curves observed for higher concentrations are well fitted to the Inokuti–Hirayama model for S = 6, which indicates that the energy transfer between the donor and acceptor is of dipole–dipole nature. The energy transfer parameter and donor to acceptor interaction increases with Dy3+ ions concentration due to increase of energy transfer from Dy3+ (donor) to unexcited Dy3+ (acceptor) ions.