Spectral characteristics of visible luminescence in Gd_2SiO_5-Lu_2SiO_5 (LGSO) solid solution crystals co-doped with Ce~(3+) and Dy~(3+)

摘要

Two single crystals of LGSO containing 1% Dy~(3+) and differing in Ce~(3+) concentration were grown by the Czochralski method. XRD examination revealed that a crystal with a nominal Ce~(3+) concentration of 3% has the C2/c structure inherent to Lu_2SiO_5 (LSO) whereas a crystal with a nominal Ce~(3+) concentration of 1% has the P2_1/c structure inherent to Gd_2SiO_5 (GSO). In both crystal structure types the excitation of Ce~(3+) ions is followed by an energy transfer to Dy~(3+) ions and resulting visible emission consists of a broad-band Ce~(3+) luminescence and of much more narrow bands of Dy~(3+) luminescence. Excitation spectra imply that the efficiency of Dy~(3+) excitation via Ce~(3+) - Dy~(3+) energy transfer is markedly higher than upon direct optical pumping into Dy~(3+) excited levels. It was observed that visible emission in the two systems differs in spectral characteristics, hence in the colour of the emitted light. Examination of optical spectra recorded with a polarized light revealed important anisotropy of transition intensities of Ce~(3+) ions in LGSO host with the P2_1/c structure.