Surface Acoustic Waves on a Sphere –Analysis of Propagation Using Laser Ultrasonics

Using the laser ultrasonic method, we investigated the distribution of surface acoustic waves (SAWs) on a sphere excited by a line source. Experimental results revealed that the SAWs were confined within a narrow path due to the balance of the diffraction and convergence effects. Moreover, the distribution had unique divergent, collimating and focussing forms, which had been predicted theoretically. These results were generally in good agreement with the results calculated using the approximate Green's function. It was shown that the distribution of SAWs is well defined by the half-aperture angle of the source and by the product of the wavenumber and the radius of the sphere.