OPTICAL-PROPERTIES OF CR-DOPED CA3SC2GE3O12 SINGLE-CRYSTALS

The absorption and luminescence properties of Cr-doped Ca3Sc2Ge3O12 ga rnet crystals were measured at temperatures ranging from 10 to 298 K. It results from the absorption spectrum that the main optically active species is Cr3+ substituting for SC3+ in octahedral low field sites. The emission properties of this material have been interpreted by cons idering T-4(2) as the only emitting level at all temperatures. The 10 K luminescence spectrum is made up of a broadband extending in the NIR region with its maximum at 13210 cm(-1); when the temperature is incr eased from 10 to 298 K, its intensity decreases to about 65% and its m aximum shifts to 13000 cm(-1). The fine structure which is present bot h in low-temperature emission and absorption spectra has been assigned as a vibronic progression in two modes with energies nu(1)=190-195 cm (-1) and nu(2)=290-295 cm(-1). The decay curves are single exponential with lifetimes ranging from 195 (10 K) to 130 (298 K) microseconds. T he temperature behaviour of the intensities and the lifetimes indicate s that the non-radiative processes are not very effective for this mat erial.