Energy Transfer Studies in Tb 3+ -Yb 3+ Co-Doped Phosphate Glasses

Detailed optical properties of Tb -Yb co-doped phosphate glasses were performed based on their emission spectra and decay measurements. Under blue excitation of Tb at 488 nm, the intensity of Yb emissions gradually enhanced upon increasing the Yb content until 1 mol% indicated an energy transfer from Tb to Yb . Otherwise, under near infrared excitation of Yb at 980 nm, these glasses exhibit intense green luminescence, which led to cooperative sensitization of the D level of Tb ions. A cooperative energy transfer mechanism was proposed on the basis of the study on the influence of Yb concentration on up-conversion emission intensity, as well as the dependence of this up-conversion intensity on near infrared excitation power. Moreover, the temporal evolution of the up-conversion emissions have been studied, which was in positive agreement with a theoretical model of cooperative up-conversion luminescence that showed a temporal emission curve with rise and decay times of the involved levels.