Transformation of valence states and luminescence of chromium ions in the YAG:Cr, Mg and GGG:Cr, Mg single crystalline films

Peculiarities of absorption spectra and recombination luminescence of Y3Al5O12 (YAG) and Cd3Ga5O12 (GGG) single crystalline films co‐doped with chromium and magnesium have been studied. The change of impurities concentration and annealing of samples in the reducing atmosphere have an influence on absorption in the visible and UV range. Using the results on absorption coefficient measurements in the band of 480 nm and in the absorption bands of Cr3+ ions, it was determined, that near 50% of the chromium ions located in octahedral sites are in the Cr4+ state in films with high chromium concentration. The investigation of thermostimulated luminescence confirms the existence of Cr2+ trap centres in the irradiated films caused by the magnesium dopant. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)