Optical absorption and photoluminescence properties of Nd 3+ doped mixed alkali phosphate glasses-spectroscopic investigations

Abstract

Spectroscopic investigations were performed on 68NH 4H 2PO 4· xLi 2CO 3(30 − x)K 2CO 3 and 68NH 4H 2PO 4· xNa 2CO 3(30 − x)K 2CO 3 (where x = 5, 10, 15, 20 and 25) glasses containing 2 mol% Nd 2O 3. Various spectroscopic parameters (Racah (E 1, E 2, E 3), spin–orbit (ξ 4f) and configuration interaction ( α)) are reported. Judd–Ofelt intensity parameters ( Ω 2, Ω 4, Ω 6) are calculated for Nd 3+ doped two mixed alkali phosphate glass matrices. From the magnitude of Judd–Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd–Ofelt 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 Nd 3+ in these mixed alkali phosphate glasses. Emission cross sections ( σ P) are calculated for the two transitions, 4G 7/2 → 4I 11/2 and 4G 7/2 → 4I 13/2 of Nd 3+ in these mixed alkali phosphate glasses. Optical band gaps ( E opt) for direct and indirect transitions are reported.