Optical absorption and luminescence properties of Nd3+ in mixed alkali borate glasses-Spectroscopic investigations

Spectroscopic investigations were performed on 67B2O3·xLi2O·(32-x)Na2O and 67B2O3.·xLi2O·(32-x)K2O (where x=8, 12, 16, 20 and 24) glasses containing 1 mol% Nd2O3. 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 (E1, E2 and E3), spin-orbit (\xi 4f) and configuration interaction (\alpha ) parameters have been calculated. Using Judd-Ofelt intensity parameters (\Omega 2, \Omega 4 and \Omega 6), total radiative transition probabilities (AT), radiative lifetimes (\tau R), branching ratios (\beta ) and integrated absorption cross sections (\Sigma) have been computed for certain excited states of Nd3+ in these mixed alkali borate glasses. From the luminescence spectra, effective line widths (\Delta\lambda eff) and stimulated emission cross-sections (\sigma p) have been reported for the three transitions 4F3/2 \rightarrow 4I9/2, 4F3/2 \rightarrow 4I11/2 and 4F3/2 \rightarrow 4I13/2 of Nd3+. 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