Material Dependence of Strain Distributions of Surface Acoustic Waves in Multilayered Thin-Film Acousto-Optic Devices

Abstract

The acoustic strain distributions in thin acousto-optic waveguides consisting of two-layered thin amorphous films on a Y-cut, X-propagation LiNbO3 substrate are studied. The theoretical relation between the elastic properties and the strain distributions in layered thin films is discussed. The strains contributing to acousto-optic interactions in the film increase as the Poisson ratio of the film material decreases. The strain amplitude in each of the layered thin films can be controlled over a wide range by suitable selection of choosing the film materials. The results give important information on improving the mode-conversion efficiency in thin-film acousto-optic devices and for designing various waveguide-type devices using acousto-optic interactions. Further, method of evaluating the elastic properties of amorphous films is discussed.