Optical properties of LaSr2Ga11O20 crystals containing Cr3+

The optical properties of trivalent chromium ions in LaSr2Ga11O20 crystals have been investigated by means of absorption, emission, excitation, and lifetime measurements for various temperatures of the sample. The data so obtained allow us to determine the values of the crystal-field parameters in the framework of the Tanabe-Sugano model for the transition-metal ion in insulating crystals and glasses. In particular, the relatively narrow emission lines indicate a high value of the crystal field. Polarized absorption and excitation measurements have allowed the assignment of the electric dipole character to the two lowest-energy transitions. From polarized excitation measurements it was possible to infer the Cr3+-ion site distortion visible in a splitting of the otherwise degenerate 4T1 level. Moreover, the effect of tempeature on the emission bands' intensities and lifetimes reveals the simultaneous presence of different competitive phenomena during the deexcitation of Cr3+ ion. © 1995 The American Physical Society