Time-resolved photoluminescence (PL) spectra of Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) crystal have been measured at various temperatures under Ce3+ 4f → 5d excitation. All time-resolved PL spectra show only a Ce3+ 5d → 4f band around 2.3 eV. Decay curves of this band consist of a fast and slow components. The temperature dependence of integrated intensities of the fast and slow components are analyzed by considering nonradiative processes starting from the ground level of an electron trap. From the results of analysis, we discuss relaxation processes of 5d electrons created under Ce3+ 4f → 5d excitation.

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Femtosecond time resolved impulsive stimulated Raman scattering has been applied to the low lying B2 mode of KH2P04 and KD2P04. The time dependent signals of both crystals show an exponential decay, meaning that both modes are relaxational in nature. The crossing angle of the exciting beams was varied to study the wavenumber dependence of the excited mode. The relaxation time of the individual dipoles of the relaxational mode was calculated to be T = 0.131 ps for KH2P04 and 1 . 0 6~s for KD2P04. Here T~ is the relaxation time of individual dipoles which is given in the equation of the relaxation time T = T~T o / ( T -TO).