Acousto-Optic Di raction by Shear Horizontal Surface Acoustic Waves in 36◦ Rotated Y -Cut X-Propagation Lithium Tantalate R. Rimeika, D. iplys and M. Shur Department of Radiophysics, Vilnius University, Vilnius, Lithuania ECSE, and PAPA, Rensselaer Polytechnic Institute, Troy, NY, USA We have investigated the acousto-optic di raction by shear horizontal surface acoustic waves in 36◦ rotated Y -cut X-propagation lithium tantalate (LiTaO3) crystals. The measurements were performed at the optical wavelength 633 nm of He Ne laser and acoustic wavelengths of 50 60 μm. The anisotropic di raction with the light polarization rotation in the transmission mode was observed. The measured and calculated values of the light incidence angle corresponding to the strongest di raction di ered signi cantly. A narrow strip of a thin metal lm deposited on the crystal surface drastically a ected the light di raction. We attribute these e ects to the conversion processes between the shear horizontal leaky surface acoustic wave and shear horizontal surface skimming bulk wave.