Infrared to visible upconversion of Nd(3+) ions in KPb(2)Br(5) low phonon crystal.

In this work we present a detailed analysis of the infrared to visible upconversion in Nd(3+)-doped KPb(2)Br(5) low phonon crystal by using both steady-state and time-resolved luminescence spectroscopy. Efficient blue, green, orange, and red emissions have been observed under excitation into the (4)F(5/2) and (4)F(3/2) states. The low phonon energy of this crystal leads to a significant reduction of the multiphonon relaxation rates which allows most of the excited states to relax radiatively. To investigate the nature of the upconversion processes, emission spectroscopy and lifetime measurements for the visible fluorescence, performed by using one photon excitation, have been compared to the upconverted emissions and lifetimes obtained under infrared pulsed excitation. The analysis of the experimental results indicates that the upconverted emissions occur via energy-transfer upconversion.