Optical avalanche in Ho:Yb:Gd2O3 nanocrystals

Intense green upconversion emission in Ho:Yb:Gd2O3 spherical nanoparticles is reported through hetrolooping enhanced energy transfer process. Different techniques used for structural characterization divulge the formation of spherical Ho:Yb:Gd2O3 crystals of diameter similar to 100 nm. Efficient energy transfer from Yb3+ -> Ho3+ ions set spherical nanocrystal to emit in the range of UV-NIR via three NIR photons absorption process. Power dependence and the temporal evolution of upconversion emission intensity suggest the occurrence of a photon avalanche process. The enhancement in emission intensity in nanophosphor sample has been explained and the photophysics involved is correlated with the unique structural properties of the crystallites formed and the time resolved spectroscopy. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622624]