Stimulated Raman scattering by transverse and longitudinal lattice vibrations in LiNbO3 and LiTaO3

Stimulated Raman scattering by longitudinal optical vibrations in crystals of the lithium niobate type was observed for the first time. The excitation thresholds of stimulated scattering by transverse and longitudinal vibrations were compared. Data on spontaneous Raman scattering were used to estimate the stimulated scattering thresholds for transverse and longitudinal vibrations and a theoretical explanation was proposed for the experimentally observed differences between lithium niobate and tantalate crystals.