OPTICAL SPECTROSCOPY AND LIGHT-INDUCED GRATINGS IN CR-3+ DOPED NONSTOICHIOMETRIC MAGNESIUM SPINEL

The results of measurements of the luminescence spectra, luminescence decay kinetics, and light-induced gratings are reported for Cr3+ doped MgO-2.5Al2O3 non-stoichiometric synthetic spinel. The results of the optical spectroscopy measurements show the existence of at least five non-equivalent Cr3+ sites in this crystal. One of the sites has a low crystal field environment, which results in a broad luminescence spectrum, characteristic of emission from the 4T2 excited level of the Cr3+ ion. The sharper emission dominates the luminescence spectra of the remaining four chromium sites associated with stronger crystal field. The results of light-induced grating measurements reveal the absence of long-range migration of the chromium excitation energy in the temperature range of 10-300 K.