Laser spectroscopy of Pr3+ ions in LiKY1-xPrxF5 single crystals

The visible luminescence of Pr3+-doped fluoride LiKY1-xPrxF5 crystals (x = 0.001, 0.01, 0.02, 0.03, 0.05, and 0.1) has been investigated as a function of concentration and temperature by using time-resolved laser spectroscopy . The temperature-dependent concentration quenching of the P-3(0) fluoresce nce in the 10-77 K temperature range can be described in the framework of a thermally activated cross-relaxation process involving the D-1(2) and H-3( 6) states. However, the single exponential character of the decays at all c oncentrations and temperatures suggests that energy migration is also prese nt in this system. The fluorescence from the D-1(2) level shows a strong co ncentration quenching for Pr3+ concentrations higher than x = 0.001 even at 4.2 K. The time evolution of the decays from the D-1(2) state for concentr ations higher than x = 0.001 is consistent with a dipole-dipole energy tran sfer mechanism. Anti-Stokes emission from the P-3(0) level following excita tion of the D-1(2) state is also studied for different Pr3+ concentrations. Analysis of the upconverted fluorescence decays supports that the mechanis m responsible for the upconvertion process is energy transfer. However, thi s process seems to be complex enough to allow for the use of a single model which could explain the behavior observed. [S0163-1829(99)04615-9].