Luminescence and laser transition studies of Dy3+:K-Mg-Al fluorophosphate glasses

Dysprosium ion doped fluorophosphate glasses with compositions of PKMAFDy: (56-x/2) P2O5+17K(2)O+8Al(2)O(3)+(15-x/2)MgO+4AlF(3)+xDy(2)O(3) (x = 0.01, 0.05, 0.1, 1.0 and 2.0 mol%) have been prepared by melt quenching technique and are characterized by optical absorption, emission spectra and fluorescence lifetime measurements. The observed bands in the absorption spectrum are analysed by using free-ion Hamiltonian (H-FI) model. The Judd-Ofelt (JO) analysis has been performed and the intensity parameters (Omega(lambda), lambda = 2, 4, 6) have been evaluated that are used to predict radiative properties. From emission spectra, the effective bandwidth (Delta lambda(eff)) and the stimulated emission cross-section (sigma(lambda(p))) were evaluated. The fluorescence decay from the F-4(9/2) level of Dy3+ ions have been measured by monitoring the intense F-4(9/2) -> H-6(13/2) transition (573 nm). The lifetimes (tau) are found to decrease with increasing concentration due to concentration quenching. The decay curves are single exponential for lower concentrations and gradually changes to non-exponential for higher concentrations. The non-exponential decay curves are well fitted to the Inokuti-Hirayama (IH) model for S = 6 which indicates that the energy transfer between the donor and acceptor is of dipole-dipole type. The systematic analysis on decay measurements reveals that the energy transfer mechanism strongly depends on concentration as well as glass composition. (C) 2008 Elsevier B.V. All rights reserved.