Pressure dependence of the 3P0→3H4 and 1D2→3H4 emission in Pr3+:YAG

Photoluminescence related to the 3P0→3H4 and 1D2→3H4 transitions of Pr3+ in YAG is measured in the pressure range from ambient to 290 kbar. The Γ1→Γ3 and Γ1→Γ4 transitions show different dependencies on pressure. All pressure shifts are negative and are smaller for the lines of lower energies for the emission from the 3P0 and 1D2 states, that were attributed to the Γ3 and Γ4 energy crossover in the ground state. To reproduce the energetic structure of the Pr3+:YAG system and dependencies of the emission energy on pressure we have used the crystal field model and considered separately isotropic compression of the Pr3+-ligand system and a non-isotropic effect described by changes of the Pr-O bond angles. The main conclusion of our investigation is that, contrary to expectation, the effect of the hydrostatic pressure is not isotropic; it changes the local bond angles of the ion–ligands system.