Peculiarities of the Ho3+→Yb3+ energy transfer in CaSc2O4:Ho:Yb

We study the effect of the energy transfer processes between Ho3+ and Yb3+ in CaSc2O4 on the emission properties in visible and IR of Ho3+ and Yb3+. The decays of the Ho3+ levels (5S2, 5F4) and 5I6 for various Yb3+ concentrations are measured. We show that, for pumping in 5F3 (at 488 nm), the total number of photons emitted by Ho3+ and Yb3+ in the wavelength domain 500-1600 nm is augmented by the presence of Yb3+. We estimate a 30% increase of the overall quantum efficiency of CaSc2O4:Ho:Yb, due to the presence of Yb3+.