Quenching of thermo-stimulated photo-ionization by energy transfer in CaAl4O7: Tb3+, Ce3+

Crystal fibers of Ce3+ and Tb3+ singly doped and co-doped CaAl4O7 were grown by the LHPG method. Photoluminescence, excitation spectra and photoconduction were measured. Thermo-stimulated photo-ionization (delocalization) of electrons from the lowest field component of the 5d excited state of Ce3+ was observed in the Ce3+ singly doped sample under excitation at 355 nm. The 5d sublevel was found to locate at 0.3 eV below the conduction band of the host. However, the thermo-stimulated photo-ionization was greatly quenched due to the fast energy transfer from the 5d sublevel to Tb3+ ions in the Ce3+/Tb3+ double doped sample.