Low temperature, infrared absorption spectra of gadolinium gallium garnet crystals doped with Ce are presented. In the region of intraconfigurational 4$f$-4$f$ transitions the spectra exhibit existence of at least two different, major Ce${}^{3+}$ related centers in the GGG crystals and also some other centers at lower concentration. The spectrum of 4$f$-4$f$ intrashell transitions of Ce${}^{3+}$ ions extends up to about 3700 cm${}^{-1}$ due to the large splitting of the ${}^2$$F_{7/2}$ excited state. In the visible region the absorption spectrum shows influence of symmetry-related selection rules. The absorption coefficient changes in the region of 4$f^1$-5$d^1$ transitions due to thermal population of the second level, belonging to the ${}^2$$F_{5/2}$ ground state. This suggests that the symmetry of the site occupied by Ce${}^{3+}$ ions, which substitute Gd${}^{3+}$, is higher than $D_2$ expected for garnet hosts.

• Received 20 August 2012

DOI:https://doi.org/10.1103/PhysRevB.87.045114