Cooperative upconversion in a new high Er-doped tellurite glass

A model for population dynamics of Er3+ in tellurite glasses with high erbium concentrations is proposed. Luminescence decay curves from transitions of I-4(13/2)--> I-4(15/2) and S-4(3/2)--> I-4(15/2) were measured experimentally. Cooperative upconversion coefficients were obtained by numerically solving the rate equations of the model to fit the population dynamics of the I-4(13/2) and S-4(3/2) levels. The cooperative upconversion coefficient for I-4(13/2)+I-4(13/2)--> I-4(9/2)+I-4(15/2) is found to be 2.74x10(-18) cm(3)/s and for I-4(11/2)+I-4(11/2) --> I-4(15/2)+F-2(7/2) is 1.09 x10(-18) cm(3)/s. The model provides a good basis for explaining the experiment data as it shows a high sensitivity to the input fitting parameters. This model can be used to analyze spectroscopic properties of Er3+ ions in glass hosts where various energy levels of Er3+ and transitions between them cannot be neglected.