Robust, high-resolution, indexed 3D slowness surfaces for Rayleigh-type waves on Lithium Niobate via parallelised Newtonian flow phase tracking

Abstract

Micro-Electromechanical System Surface Acoustic Wave (MEMS SAW) devices are key technological enablers in RF telecommunications filters, inertial systems and biosensors. Recent developments in Focused SAW (FSAW) device design demand high quality, high resolution dispersion data for multiple in-plane directions, typically presented as a slowness curve, to facilitate design. Very few slowness curves are available in the literature for free surfaces not aligned to the crystallographic axes except in a few special cases. The first major novelty in the present work is a bespoke computational approach to solving this problem with a distinct theoretical basis. After a brief summary of the motivation, the mathematical formulation and its theoretical footing are outlined. The most important algorithms are given as pseudocode, and source code, datasets and extended visualisation available online are referenced. The structure of the method is illustrated via application to the bulk wave problem. The model is then applied to Lithium Niobate to generate new results characterising SAW propagation velocity for all in-plane directions over one full circle of plane inclinations. These results are presented as a two-dimensional velocity surface. This new data constitutes the second area of novelty herein. Finally, the applicability of the work to FSAW design is indicated by examining the RMS variation of propagation velocity for different cut plane inclinations.