A theoretical elucidation for the experimentally observed backward displacement of waves reflected from an interface having superimposed periodicity

Abstract

It has been shown experimentally by Breazeale and Torbet [M. A. Breazeale and M. A. Torbett, Appl. Phys. Lett. 29(8), 456–458 (1976)] that a backward beam displacement can occur when a beam is reflected from an interface having superimposed periodicity. The angle at which the phenomenon occurs was predicted by Bertoni and Tamir [H. L. Bertoni and T. Tamir, Appl. Phys. 2, 157–172 (1973)] with a classical approach dated before the inhomogeneous waves era. However, during that era it has been shown by many scientists that the ultimate theory to describe critical phenomena, such as the generation of surface waves or the existence of a beam displacement, is the inhomogeneous wave theory. In the present research, one applies the inhomogeneous wave theory and shows that the theory predicts extremely well the phenomenon of backward displacement when a bounded beam reflects from a periodically rough surface. The agreement reaches far beyond a prediction of the angle of occurrence. One is able to simulate the entire physical phenomenon as it happens in the experiments of Breazeale and Torbet. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]