Yb3+ ion in calcium niobium gallium garnet crystals:: Nearest neighbor environment and optical spectra

We have studied inhomogeneously broadened optical spectra of the Yb3+ ion in calcium niobium gallium garnet crystals using selective laser excitation, time-resolved luminescence spectroscopy, and F-2(5/2) luminescence decay measurements under excitation in different portions of the absorption spectrum. We have identified spectral features due to individual optical centers differing in excitation and luminescence wavelengths and excited-state lifetime. Tentative structures of the optical centers responsible for the inhomogeneous broadening of the spectra are described.