title: [The upconversion mechanisms for the red and green emissions in Er3+ doped and Er3+ -Yb3+ codopoed fluoride materials based on experiment].
abstract: The rare earth Er3+ doped and Er3+ -Yb3+ co-doped fluoride samples were prepared. Under 980 nm laser excitation, the intense red (650 nm) and green (545 nm) upconversion luminescence was obtained corresponding to the transitions 4S3/2, 2H11/2--4I15/2 and 4F9/2--4I15/2, respectively. For the Er3+ -Yb3+ co-doped fluoride samples, it was found that the ratio of the red upconversion luminescence to the green one decreases as the Er3+ concentration increases. The dependence of upconversion intensities on excitation power indicates that two-photon absorption processes are responsible for the upconverted luminescence. The possible upconversion mechanisms of the red and green emissions are discussed based on the energy-matching conditions and the quadratic dependence on excitation power.
authors.affiliation: Physics Department of Xiangtan University, Xiangtan 411105, China.
authors.forename: Jun-hui
authors.initials: JH
authors.lastname: Lei
authors.forename: Si-guo
authors.initials: SG
authors.lastname: Xiao
authors.forename: Lei
authors.initials: L
authors.lastname: Yan
authors.forename: Zheng-wei
authors.initials: ZW
authors.lastname: Liu
mesh_terms: D004871:Erbium / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D007834:Lasers; D049449:Luminescence; D008163:Luminescent Measurements / Q000379:methods; D013050:Spectrometry, Fluorescence; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D004871:Erbium; D015018:Ytterbium; D005459:Fluorides