The effect of mixed alkalis on the absorption and fluorescence properties ofHo3+ ions in borate glasses

Abstract

Spectroscopic properties of Ho3+ in 67B2O3·xLi2O ·(32−x)Na2O,67B2O3·xLi2O ·(32−x)K2O and67B2O3·xLi2O ·(32−x)Cs2O (wherex = 8, 12, 16,20 and 24) glasses were investigated on the basis of Judd–Ofelt theory. Various spectroscopic parameters(E1,E2,E3,ξ4f,α andβ) and Judd–Ofeltintensity parameters (Ω2, Ω4 andΩ6) are calculatedas a function of x in the three glass matrices. The obtained Judd–Ofelt intensity parameterΩ2 increases with the addition of a second alkali and also shows minima or maxima atx = 16–20 mol % in the above glasses. Using Judd–Ofelt intensity parameters(Ω2,Ω4 andΩ6), radiative transitionprobabilities (AT),radiative lifetimes (τR), branching ratios (β) and integrated absorption cross sections(Σ) have been calculated for certain excited states ofHo3+. The non-radiative transition rates of different excited states ofHo3+ arealso estimated from ‘energy gap law’. From the luminescence spectra, stimulated emission cross-sections(σp) have been obtained for the two transitions and of Ho3+. The trend of all these parameters observed as a function ofx in these glass systems have been discussed, keeping in mind the effect of mixed alkalis.