Optical absorption and luminescence properties of Nd 3+ in mixed alkali borate glasses—Spectroscopic investigations

Abstract

Spectroscopic investigations were performed on 67B 2O 3· xLi 2O·(32- x)Na 2O and 67B 2O 3.· xLi 2O·(32- x)K 2O (where x=8, 12, 16, 20 and 24) glasses containing 1 mol% Nd 2O 3. Covalency was studied as a function of x using Judd-Ofelt intensity parameters that are related to the ligand field symmetry and the degree of bond covalency. Results show that covalency increases when the third component is added to the binary borate glass matrix. Various spectroscopic parameters like Racah ( E 1, E 2 and E 3), spin–orbit ( ξ 4f) and configuration interaction ( α) parameters have been calculated. Using Judd-Ofelt intensity parameters ( Ω 2 , Ω 4 and Ω 6 ), total radiative transition probabilities ( A T), radiative lifetimes ( τ R), branching ratios ( β) and integrated absorption cross sections (∑) have been computed for certain excited states of Nd 3+ in these mixed alkali borate glasses. From the luminescence spectra, effective line widths (Δ λ eff) and stimulated emission cross-sections ( σ p) have been reported for the three transitions 4F 3/2→ 4I 9/2, 4F 3/2→ 4I 11/2 and 4F 3/2→ 4I 13/2 of Nd 3+. Among all the glasses studied, lithium sodium glass with x=12 and lithium potassium glass with x=20 show high absorption and emission cross-sections.