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Er3+ doped Y2O3 and Nb2O5 modified germanate glasses with different Er3+ concentrations were prepared. J-O intensity parameters were computed to estimate the structural changes due to the additions of Y2O3 and Nb2O5. The main mid-infrared spectroscopic features were investigated. To shed light on the observed mid-infrared radiative behavior, 975 nm and 1.53 μm emission spectra along with their decay lifetimes were also discussed. Moreover, the energy transfer processes of 4I11/2 and 4I13/2 level were quantitatively analyzed. In view of the experimental lifetimes, the simplified rate equation was utilized to calculate the energy transfer upconversion processes of upper and lower laser level of 2.7 μm emission. The theoretical calculations are in good agreement with the observed 2.7 μm fluorescence phenomena. Finally, the stimulated emission and gain cross sections were calculated and the results indicate that Er3+ doped germanate glasses have great potential for mid-infrared application.

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Er3+ doped oxyfluoride tellurite glasses have been prepared. Three Judd-Ofelt parameters Ωt (t = 2, 4, 6) and radiative properties are calculated for prepared glasses. Emission characteristics are analyzed and it is found that prepared glasses possess larger calculated predicted spontaneous transition probability (39.97 s−1), emission cross section σem (10.18 × 10−21 cm2) and σem × Δλeff (945.32 × 10−28 cm3), corresponding to the 2.7 μm emission of Er3+: 4I11/2→ 4I13/2 transition. The results suggest that the prepared glasses might be appropriate optical material for mid-infrared laser application. Moreover, rate equation analysis which is rarely used in bulk glass has been carried out to explain the relationship between emission intensity and Er3+ concentration. The calculation results show that with the increment of Er3+ concentration, the energy transfer up-conversion rate of 4I13/2 state increases while the rate of 4I11/2 state reduces, resulting in the change of 2.7 μm emission.