Determination of energy transfer and upconversion constants for Yb

The energy transfer and cooperation upconversion processes are investigated in Yb3+/Er3+ codoped phosphate glass. Based on the measured curves of output power versus incident power, the laser and spectroscopic parameters of the glass are fitted and analyzed. We focus on the resonant energy transfer constant k from Yb3+ to Er3+ as well as the cooperation upconversion coe±cient Cup from 4I13/2 of Er3+. The fitt