Efficient visible up-conversion emission in Pr3+- and Er3+-doped aluminum fluorophospate glasses

Intense upconversion of yellow-to-blue, in Pr3+-doped, and green-to-blue in Er3+-doped aluminum fluoride glasses is reported. Pulsed excitations inside the 3H4->1D2 absorption band of Pr3+ results in blue emission which is ascribed to the 3P0->3H4 transition. We found that the temporal evolution of the upconverted fluorescence is characterized by rise and decay times depending on Pr3+ concentration. The upconversion mechanism is a two step process due to the energy transfer involving a pair of Pr3+ ions. The data indicate a high solubility of the Pr3+ ions without clustering at the doping level between 0.1-1% mol Pr3+. Measurements performed in Er3+-doped glasses indicate a good quantum yield of the upconversion emission confirming the high solubility of Er3+ ions in the aluminum fluoride glasses.