Energy Transfer to Pr$^{3+}$ Ions in Pr:Lu$_{3}$ Al$_{5}$O $_{12}$ (LuAG) Single Crystals

Single crystals of LuAG doped with Pr
³⁺
ions (0.2 mol%) are grown by the micro-pulling-down (mu-PD) method with an RF heating system. The as-grown crystals are confirmed to be of garnet-type structure with the space group of Ia3d (230). The emission-excitation spectra and luminescence decay kinetics are measured in the temperature range of 5-310 K by using synchrotron radiation as an exciting light source. The intrinsic luminescence is observed at 250 nm at low temperatures. Four emission bands at 308, 325, 360, and 380 nm are ascribed to the 5d-4f transitions of Pr
³⁺
ions. From the decay kinetics measurements, it is pointed out that there exist two kinds of energy transfer mechanisms from the host LuAG lattice to the Pr
³⁺
ions. The mechanisms of energy transfer are discussed in connection with the formation of substitution-type defects.