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Spectroscopy of gadolinium gallium garnet doped with cerium under high hydrostatic pressure

Studies of the spectroscopic properties of Ce<sup>3+</sup> dopant in bulk Gd<inf>3</inf>Ga<inf>5</inf>O<inf>12</inf>:Ce crystal under pressure are presented. In spite of strong inter-shell 4f → 5d absorption bands at ambient pressure the cerium luminescence in Gd<inf>3</inf>Ga<inf>5</inf>O<inf>12</inf> is entirely quenched even at low temperature. It has been shown that applying pressure allows for recovering the 5d → 4f radiative transitions. Further increase of pressure improves the emission efficiency. This effect is analyzed in terms of two possible phenomena: (i) by pressure-induced electronic crossover of the excited 5d energy level of the Ce<sup>3+</sup> with the conduction band bottom of host crystal, and (ii) by decrease of electron-lattice coupling with increasing pressure, resulting in reducing of Stokes shift and non-radiative transitions between the low vibrational levels of the 5d state and high vibrational levels of the ground 4f state.