Further studies of the scattering of a Gaussian beam from a fluid–solid interface

Abstract

Our earlier study [J. Pott and J. G. Harris, J. Acoust. Soc. Am. 76, 1829–1838 (1984)] of the reflection and refraction, at a plane fluid–solid interface, of a Gaussian beam is continued. When the angle of incidence approaches the angle at which the compressional wave is critically refracted, a lateral wave is excited both in the fluid and in the solid. In the fluid, this wave interferes with the reflected beam, making it appear shifted and distorted. A second lateral wave is excited in the fluid when the angle of incidence nears that at which the shear wave is critically refracted. However, this angle is usually quite close to the Rayleigh angle. Thus the nearly coincident excitation of a leaky Rayleigh wave (examined in our earlier paper) masks any effect the lateral wave has. But even for angles of incidence not near these three critical angles, the axis of the reflected beam is slightly rotated and displaced. The refracted beams (examined in our earlier paper) spread quite rapidly in the solid, but, by using a thin lens to focus the incident beam, this spreading can be reduced somewhat.