We have investigated the spectroscopic properties of Pr 3+ ions in LiLuF 4 laser host doped with 0.5% Pr 3+ ions as a function of temperature. We obtained the luminescence spectra by exciting selectively the sample at 439nm into the 3 P 2 level and at 593nm into the 1 D 2 level. With excitation in the 3 P 2 level we obtained emission only from the 3 P 0 level but not from the 1 D 2 level at all temperatures between 24 and 300K. With excitation into the 1 D 2 level we observed the luminescence emitted by the same level and a strong blue up-conversion emission from the 3 P 0 level. We used the decay pattern inspection to assign spectral lines to specific radiative transitions and to study the dynamics of the excited ions in the crystal. Under direct excitation, the 1 D 2 decay curve is nonexponential at all temperatures, whereas the 3 P 0 decay is exponential only at low temperatures. The experimental data indicate that the 3 P 0 level is populated via upconversion due to mainly energy transfer.
