Analysis of energy transfers between Tb^3+ and Yb^3+ codoped in borosilicate glasses

Energy transfer analyses are performed on Tb3+ and Yb3+ codoped in borosilicate glasses to assess their potential as gain media for green lasers and amplifiers under the 0.98 μm band pumping. Based on experimental observations using the samples highly codoped with Tb3+ and Yb3+, a rate equation model of energy transfers between Tb3+ and Yb3+ is constructed considering the four types of energy transfers processes; (i) the cooperative energy transfer upconversion, (ii) the phonon-assisted energy transfer from Tb3+ to Yb3+, (iii) the cooperative cross relaxation, and (iv) the phonon-assisted energy transfer from Yb3+ to Tb3+. The rate equation model can simulate the experimental emission dynamics of Tb3+ and Yb3+ codoped samples well. It is clarified that a practical signal gain at 0.54 μm can be obtained in Tb3+-Yb3+ codoped fiber under the 0.98 μm band pumping.