Upconversion luminescence of Er3+/Yb3+-codoped natrium-germanium-bismuth glasses

The absorption and upconversion fluorescence spectra of a series of Er3+/Yb3+-codoped natrium-germanium-bismuth glasses have been studied. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. At room temperature, an upconversion efficiency of 6.1×10−2 has been obtained for the green emission from the glass with 0.5 wt% Er2O3 and 3.0 wt% Yb2O3 pumped by 980 nm radiation with an intensity of 270 W/cm2. And the “standardized” efficiency for green upconversion light is higher than that reported in lead-germanate, lead-tellurite-germanate, and silicate glasses. The results indicate that the Er3+/Yb3+-codoped natrium-germanium-bismuth oxide glass may be a potential material for developing upconversion optic devices.