Focusing of Surface Acoustic Wave on a Piezoelectric Crystal

Abstract

We investigate the focusing phenomena of a surface acoustic wave (SAW)field generated by a circular-arc inter-digital transducer (IDT) on apiezoelectric crystal. A rigorous vector field theory of surfaceexcitation on the crystal we developed previously is used to evaluatethe convergent SAW field instead of the prevalent scalar angularspectrum used in optics. The theoretical results show that theanisotropy of a medium has great impact on the focusing properties ofthe acoustic beams, such as focal length and symmetrical distributionsnear the focus. A dark field method is used in experiment to observe thefocusing of the SAW field optically. Although the convergent phenomena ofSAW field on the anisotropic media or piezoelectric crystals are verycomplicated, the experimental data are in agreement with those from therigorous theory.