Meandering collimated beam of surface acoustic waves on a trigonal crystal ball

To fully exploit high-quality piezoelectric crystals in acoustic wave devices, it is necessary to remove limitations not related to the crystal quality. Among them, the "diffraction loss" is most serious. Previously, we have developed the ball surface acoustic wave (SAW) sensor using crystal ball. However, because of the piezoelectric crystal's strong anisotropy, we could not control the propagation route of SAWs on a ball. Here, we report a discovery that the beam propagates along a meander route, identical at every turn. Consequently, we succeeded in completely removing the diffraction loss. Since it can fully exploit the quality of crystals, it will stimulate progress of crystal technology.