Surface acoustic waves on a sphere with divergent, focusing, and collimating beam shapes excited by an interdigital transducer

Abstract

The surface acoustic wave (SAW) device on a ball is expected to provide high-performance sensors. Since we must deal with three-dimensional wave fields for precise design of ball SAW devices, numerical methods, such as the finite element method, will require too many elements. Therefore, we applied an analytical solution to a practical calculation of the full-field acoustic waves. For an IDT aperture of 6° and 80° with a wave number parameter of 45, the SAW has a divergent beam and a focusing beam, respectively. For an intermediate aperture of 30°, the SAW forms a collimating beam. This calculation confirmed the possibility of an extremely sensitive sensor with diffraction-free SAWs without disturbance by spurious bulk waves.