Finite-element solution of Rayleigh-wave scattering from reflective gratings on a piezoelectric substrate.

A numerical approach that combines the finite-element method (FEM) and the analytical method is discussed. To treat a large periodic structure in which a repetition of complicated components arises, the substructure method is introduced. As a result, the mutual interaction between surface waves and bulk waves is automatically taken into account over the entire discontinuity region. In addition, the FEM with Hermitian line elements is introduced to compute the propagation constants and field distributions of propagating modes in uniform piezoelectric waveguides that are needed for constructing analytical solutions. To show the validity and usefulness of this approach, examples for various metallic gratings on 128 degrees Y-X LiNbO(3) substrate are computed. The computed results are in approximate agreement with the earlier experimental results.