ONE-COLOR SEQUENTIAL PUMPING OF THE 4F5D BANDS IN PR-DOPED YTTRIUM-ALUMINUM-GARNET

We report on a method for populating the 4f5d bands in Pr-doped yttrium aluminum garnet (Pr3+ : YAG) through a one-color two-photon absorption process. Broad ultraviolet emission (between 300 and 400 nm) is obtained by pumping the crystal with a source between 470 and 490 nm. The dynamics of the two-photon process is studied by monitoring the transient rise and decay of the fluorescing populations under chopped CW excitation. The transient data show that the two photons are absorbed sequentially with either the P-3(1) or P-3(0) level acting as a metastable intermediate state. An excitation spectrum for the 314 nm emission from the lowest 4f5d band is compared to the excitation spectrum for the 615 nm emission from the P-3(1) and P-3(0) levels. Strong enhancement in UV emission occurs when the laser is resonant with transitions to the P-3(1) or P-3(0) levels. A model for the dynamics of the sequential two-photon pumping process is proposed. The model predicts that the population of UV fluorescing ions is indirectly controlled by energy transfer processes involving ions in the 1D2 state.