Lenses and graded films for focusing and guiding acoustic surface waves
- 1 January 1970
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in Proceedings of the IEEE
- Vol. 58 (8) , 1230-1237
- https://doi.org/10.1109/proc.1970.7899
Abstract
Two novel schemes for guiding acoustic surface waves along curved paths on isotropic substrates are described. One involves the deposition of a slowing film of graded thickness along the intended path on a dielectric substrate. Paraxial-ray equations are developed to describe the ray paths adjacent to the axis of the guiding film, which are determined by the slowing factor resulting from a variable-thickness deposited film. Diffraction is taken into account through an approximation developed by Pierce for optical beams. It is shown that very thin films are sufficient for a substantial amount of directional control. The other guidance system employs a series of lenses in analogy with the lens guides developed for millimeter waves and optical beams. Some comments are made about thin-film lenses and the theory is developed for the focusing action of a lens formed by a spherical depression in (or protrusion from) the surface of a substrate. A simple analog for determining ray paths over generally nonplanar surfaces is described and applied to nonspherical depressions to evaluate their focusing properties.Keywords
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