Luminescence and optical absorption properties of Nd3+ ions in K-Mg-Al phosphate and fluorophosphate glasses

Absorption and emission properties and fluorescence lifetimes for the F-4(3/2) -> I-4(11/2) transition of Nd3+ ions embedded in P2O5-K2O-MgO-Al2O3 (PKMA)-based glasses modified with AlF3 and BaF2 are reported at room temperature. The observed energy levels of Nd3+ ions in these glasses have been analysed through a semi-empirical free-ion Hamiltonian model. The spin-orbit interaction and net electrostatic interaction experienced by the Nd3+ ions follow the trend as PKMA > PKMA + AlF3 > PKMA + BaF2 glasses. Judd-Ofelt analysis has been carried out on the absorption spectra of 1.0 mol% Nd3+-doped glasses to predict the radiative properties for the fluorescent levels of the Nd3+ ion. Branching ratios and stimulated emission cross-sections show that the F-4(3/2) -> I-4(11/2) transition of the glasses under investigation has the potential for laser applications. The Inokuti-Hirayama model has been applied to investigate the non-radiative relaxation of the Nd3+ ion emitting state, F-4(3/2). Based on the decay curve analysis, concentration quenching of the F-4(3/2) emission has been attributed to a cross-relaxation process between the Nd3+ ions.