Abstract: The collinear surface acoustic wave properties that determine the induced grating parameters have been investigated using a rigorous modeling of the surface acouseic wave propagation in multiplayer. The guided-to-leaky mode conversion by the induced diffraction grating from surface acouseic wave is analyzed using a generalized multimode formulation of the coupled mode theory. Mode conversion efficiency has been calculated as functions of acoustic frequency, interaction length, guiding layer thickness, and acoustic drive power density.