Er-Yb Codoped Ferroelectrics for Controlling Visible Upconversion Emissions

Abstract

Under a 980 nm laser pumping, quenching of green upconversion (UC) emission accompanied with enhancement of red UC emission observed was dominated by the energy back-transfer (EBT) process in Er(3+) and Yb(3+) codoped PbTiO(3), BaTiO(3), and SrTiO(3) polycrystalline powders. The efficiency of the EBT process depends not only on Yb(3+) concentration but also on level match of the doped Er(3+) and Yb(3+) ions caused by the crystal fields with different symmetries. Our UC emission spectra and X-ray diffraction confirm that the centrosymmetric crystal field arising from reducing tetragonality causes level match of transition (4)S(3/2) -> (4) I(13/2) of Er(3+) and (2)F(7/2) -> (2) F(5/2) of Yb(3+). This level match is responsible for enhancing red UC emission.