Intense red upconversion emission and energy transfer in Yb3+/Ho3+/Er3+:CaYAlO4

In this paper, we report on the intense red up-conversion emission in Yb3+/Ho3+/Er3+: CYA crystal. The fluorescence spectra in three different doped crystals (Er3+: CYA, Ho3+/Er3+: CYA and Yb3+/Ho3+/Er3+: CYA) have been measured and compared in a full emission range (visible, near-infrared and mid-infrared). The energy transfer and up-conversion emission mechanisms were discussed. Results show with the doping of Yb3+ ion, the intensity of red emission in Yb3+/Ho3+/Er3+: CYA crystal become much stronger, about 10 times, than that of Ho3+/Er3+: CYA, and 30 times than that of Er3+: CYA. The energy transfer efficiency of Yb3+ to Ho3+, Er3+ ion was calculated to be 0.727 which indicates that Yb3+ ion transfers a majority of its energy to Ho3+, Er3+ ion and finally results in the strong red up-conversion emission in Yb3+/Ho3+/Er3+: CYA crystal.