Energy transfer between Yb3+ and Er3+ in barium gallogermanate glass

Spectroscopic properties of Er3+/Yb3+ codoped barium gallogermanate glass demonstrate that an efficient energy transfer from Yb3+ to Er3+ ions occurs while the back energy transfer from Er3+ to Yb3+ ions cannot be ignored. Based on the rate equations of electron transitions, the forward energy transfer Yb3+(F25/2)+Er3+(I415/2)→Yb3+(F27/2)+Er3+(I411/2) and the back transfer Er3+(I411/2)+Yb3+(F27/2)→Er3+(I415/2)+Yb3+(F25/2) coefficients were calculated to be 9.2×10−17 cm3 s−1 and 1.1×10−17 cm3 s−1, respectively. Also the energy transfer upconversion coefficient Yb3+(F25/2)+Er3+(I411/2)→Yb3+(F27/2)+Er3+(F27/2) was determined to be 1.1×10−16 cm3 s−1. The calculated results show that a population inversion between the I413/2 and I415/2 levels can be attained at a low pumping flux of around 1.7×1022 cm−2 s−1, while the inversion threshold between the S43/2 and I415/2 levels is about 30 times higher when pumped by 980 nm laser diode. With increasing pump flux the back energy transfer probability becomes larger and when the pump flux is more than 2.0×1022 cm−2 s−1, the back energy transfer probability dominates the forward energy transfer probability.