Nd3+-Cr3+ Pairs In Gd3sc2ga3o12 Garnet Crystals

Several crystals of Gd3SC2Ga3O12 (GSGG) with different concentrations of Nd3+ and Cr3+ ions have been grown using the Czochralski technique. Optical absorption and site-selective luminescence spectra have been measured in the wavelength range 350-900 nm at low temperatures (15-77 K). These spectral reveal the presence of Nd3+ ions in two different crystal field sites. Some Nd3+ ions substitute for Gd3+ ions in unit cells in which the central octahedral site is occupied by Sc3+ ions. However, in a significant fraction of unit cells containing Nd3+ the central octahedral site is occupied by Cr3+ ions. These centres are labelled Nd3+ (SC3+) and Nd3+ (Cr3+), respectively. The spectroscopic characteristics of these perturbed Nd3+ centres are reported and their relevance to the enhanced Nd3+ laser efficiency of Cr3+:Nd3+:GSGG relative to Nd3+:GSGG is discussed.