Surface acoustic wave scattering from steps, grooves, and strips on piezoelectric substrates

The paper studies, by the finite element method, the reflection of surface acoustic waves from single obstacles of regular shapes on the surface of piezoelectric materials. The so-called perfectly matched layer is used to truncate the computational domain. The following types of imperfections are considered: single steps, grooves, and projections, as well as metallic strips overlaying the substrate or inset into it. The absolute values and the phases of the reflection coefficients are computed for YZ and 128°YX LiNbO₃ substrates as functions of the height-to-wavelength and the width-to-wavelength ratios. In addition, the reflectivity of gratings comprising a finite number of grooves or electrodes is computed and compared with the analytic estimations based on the coupling-of-modes theory.