Optical absorption and photoluminescence properties of Er 3+ doped mixed alkali borate glasses

Abstract

An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er 2O 3 in mixed alkali borate glasses of the type 67.8B 2O 3· xLi 2O(32 − x)Na 2O, 67.8B 2O 3· xLi 2O(32 − x)K 2O and 67.8B 2O 3· xNa 2O(32 − x)K 2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H 3BO 3, Li 2CO 3, Na 2CO 3, K 2CO 3 and Er 2O 3 (950–1100 °C, 1.5–2 h) between two brass plates. Spectroscopic parameters like Racah ( E 1, E 2 and E 3), spin-orbit ( ξ 4f) and configuration interaction ( α) parameters are deduced as function of x. Using Judd–Ofelt theory, Judd–Ofelt intensity parameters ( Ω 2, Ω 4 and Ω 6) are obtained. Radiative and non-radiative transition rates ( A T and W MPR), radiative lifetimes ( τ R), branching ratios ( β) and integrated absorption cross-sections ( Σ) have been computed for certain excited states of Er 3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er 3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses.