Spectroscopic and 1.06 μm laser properties of Nd3+-doped K–Sr–Al phosphate and fluorophosphate glasses

Optical absorption, fluorescence and decay curves for the 4F3/2 level of Nd3+ ions in phosphate (P2O5–K2O–SrO–Al2O3) and fluorophosphate (P2O5–K2O–SrO–Al2O3–AlF3 and P2O5–K2O–SrO–Al2O3–BaF2) glasses doped with three concentrations (0.1, 1.0 and 2.0 mol%) of Nd3+ ions have been investigated. The Judd–Ofelt (JO) theory has been applied to the absorption spectra of 1.0 mol% Nd3+-doped glasses to derive JO intensity parameters which are in turn used to calculate the radiative properties of the Nd3+ ion fluorescent levels. The assigned energy level data of Nd3+ (4f3) ions are analysed in terms of a parametrized free-ion Hamiltonian model that consists of 20 interaction parameters of atomic nature. The stimulated emission cross section and branching ratios have been calculated using the emission spectra. The relatively higher branching ratio for 4F3/2 → 4I11/2 transition shows the suitability of these glasses for laser application. It is interesting to note that the measured decay curves of the 4F3/2 level remain nearly single exponential even for higher Nd3+ ion concentration but with shortening of lifetime.