Fluorescence and Judd–Ofelt analysis of Nd 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 (ξ_4f) 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 (A_T), radiative lifetimes (τ_R), 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 (σ_p) have been calculated for the two transitions, ⁴G_7/2 → ⁴I_13/2 and ⁴G_7/2 → ⁴I_11/2 of Nd³⁺ in all these glass matrices. From the absorption spectra, the optical band gaps (E_opt) 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.