1.55 μm emission and upconversion properties of Er3+-doped oxyflurotellurite glasses

Oxyfluorotellurite glasses doped with different concentrations of Er3+ ions have been prepared and characterized. Strong infrared fluorescence at 1.55 μm and efficient green and red upconversion fluorescence were observed under 975 nm excitation. The half maximum of the 1.53 μm emission varies from 67 to 93 nm with change in Er3+ ions concentration. Decay curves of this emission remain single exponential but with reduced lifetimes with increase in Er3+ ions concentration. Concentration quenching of lifetime of the 4I13/2 level has been analyzed with the theory developed by Auzel et al. [F. Auzel, F. Bonfigli, S. Gagliari, G. Baldacchini, J. Lumin. 94–95 (2001) 293] and is found to be diffusion limited. A mechanism has been proposed to explain the upconversion process.