Fluorescence and Judd–Ofelt analysis of Nd3+ doped P2O5–Na2O–K2O glass

Sodium potassium phosphate glass consisting different Nd2O3 concentrations have been prepared to study the effect of Nd3+ concentration on optical absorption and fluorescence properties. From the absorption spectra, Racah (E1, E2, E3), spin-orbit (ξ4f) and configuration interaction (α) parameters are calculated and reported for all the Nd3+ doped glasses. Judd–Ofelt intensity parameters (Ω2, Ω4, Ω6) are evaluated and these parameters are used to study the covalency as a function of Nd3+ concentration. Results show that covalency decreases with the increase of Nd3+ concentration. By using these three intensity parameters, total radiative transition probabilities (AT), radiative lifetimes (τR), branching ratios (β) and integrated absorption cross-sections (Σ) have been computed for certain excited states of Nd3+ in these mixed alkali phosphate glasses for all the concentrations. From the fluorescence spectra, peak stimulated emission cross-sections (σp) have been calculated for the two transitions, 4G7/2 → 4I13/2 and 4G7/2 → 4I11/2 of Nd3+ in all these glass matrices. From the absorption spectra, the optical band gaps (Eopt) for both direct and indirect transitions have been obtained. All these spectroscopic parameters are compared for different Nd3+ concentrations. From these studies, a few transitions are identified for laser excitation among various transitions.