Absorption spectra of different composition of tellurite glasses were analyzed in order to estimate their lasing properties. Composition of the investigated tellurite glasses are: 55TeO2-(43-x)ZnO-2Bi2O3-xEr2O3(x = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mol%). Glasses absorption spectra and density were measured at room temperature using UV-VIS-NIR Spectrophotometer and pycnometer, respectively; while their refractive index were measured by implying Brewster’s angle method. Lasing performance of glasses were then analyzed using Judd-Ofelt theory in order to obtain line strength (S), Judd-Ofelt parameters (Ωt, t = 1, 2, 3), and radiative life-times (τ). It is seen that incorporating Er3+ions of up to 2.5 mol% resulted in decreasing the radiative lifetime of electrons sitting at4I11/2. From Judd-Ofelt parameters analysis it can be concluded that these tellurite glasses tend to have the covalence nature of Er-O bond and thus represents the asymmetry around the Er3+ions site.
