title: 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+) co-doped 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)S3/2-->I13/2 of Er(3+) and (2)F7/2-->(2)F5/2 of Yb(3+). This level match is responsible for enhancing red UC emission.
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Tahsueh Rd., Hsinchu, 30050, Taiwan.
authors.forename: Tung-Ching
authors.initials: TC
authors.lastname: Huang
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Hsieh
mesh_terms: D004560:Electricity; D004871:Erbium / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014025:Titanium / Q000737:chemistry; D014961:X-Ray Diffraction; D015018:Ytterbium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D004871:Erbium; D014025:Titanium; D015018:Ytterbium