Crystal growth and optical properties of Cr4+:Li2TiGeO5

Crystal growth and optical properties of Cr4+ centers in Li2TiGeO5 single crystals were investigated. Polarized absorption spectra at low and room temperature indicate a lowering of symmetry of the local environment of the Cr4+ ion from Td to C2 group of symmetry. The crystal field parameter Dq and the Racah paprameter B were determined to be Dq=930 cm−1, B=510 cm−1, and Dq/B=1.8. Emission spectra show wideband fluorescence from 1100 to 1600 nm with the maximum at 1200 nm. The lifetime of the metastable level decreases from 62 μs at 77 K to 6 μs at 300 K, indicating strong nonradiative quenching and a quantum efficiency of less than 10%.