Upconversion Emission of Infrared Excited Er3+-Doped Transparent Glass Ceramics Containing CaF2 Nano-Crystals

Upconversion luminescence of Er3+-doped SiO2-Al2O3-CaO-NaF-CaF2 transparent glass ceramics under 980 nm excitation was investigated. XRD and TEM experiments revealed the homogeneous distribution of CaF2 nano-crystals among the glassy matrix. Intense red upconversion signal was recorded and its intensity increased with the increasing of heating temperature and Er3+-doping level at the range of 0.1 to 1.0 mol%. When Er3+ doping reached 2 mol%, the concentration quenching effect appeared. All these results could be due to the incorporation of Er3+ ions into precipitated CaF2 nano-crystals. The quadratic pump power dependence of the upconversion luminescence intensity indicated that the transition mechanism of the red emission was due to two-photon absorption processes.