Observation of avalanche upconversion emission in Pr:Y2O3 nanocrystals on excitation with 532 nm radiation

In this paper we report the two photon upconversion process in nanosize Pr:Y2O3 crystals on excitation with 532 nm photon at room temperature. Upconversion emission intensity shows an abrupt change at the critical pump threshold. On the basis of the temporal evolution of the intermediate state population and power-dependence studies, it is concluded that the significant variation in upconversion emission intensity is due to the photon avalanche process.