Site-Selective Spectroscopy and Infrared-to-Visible Upconversion in a Nd3+-Doped Pb5Al3F19 Crystal.

Abstract In this work, we analyzed the spectroscopic features of the absorption and emission of Nd 3+ in a fluoroaluminate Pb 5 Al 3 F 19 crystal. Two main crystal field sites were identified for the rare earth in this crystal which may correspond to the two different crystallographic sites of Pb 2+ . Infrared-to-visible and -ultraviolet upconversion, under continuous wave and pulsed laser excitation, was observed at room and low temperatures. Analysis of the steady-state excitation spectra and of the decays of the upconverted emissions shows that the most likely mechanism for the observed upconversion emissions is an energy-transfer upconversion (ETU) process.