Phonon-assisted laser transitions and energy transfer in rare-earth laser crystals

An extensive study of energy transfer and phonon interaction in rare earth doped LiYF4 has been conducted. The trivalent rare earth ions Pr, Nd, Dy, Ho, Er, Tm and Yb were used as the optically active ions. Y2Ti2O7, also doped with rare earth ions, was examined. A new technique for investigating energy transfer was used. Crystals with high enough concentration of sensitizer and activator ions to assure near neighbor pairs were used to measure transfer rates as a function of energy gap. An exponential dependence on energy gap was found. Efficient transfer was also observed in Y2Ti2O7, which has inversion symmetry at the rare earth site and therefore no allowed electric dipole transitions. (Author)