Analysis of surface wave formation over a grating surface with bounded beams

Abstract

It had been demonstrated previously that homogeneous plane waves could not excite effective surface wave over periodic surface structures at low frequencies. In this work, acoustic surface wave over a periodic surface is predicted under limited source incidence (e.g., Gaussian beam). A comblike grating surface is considered in the analysis, for which a theoretical model for predicting the scattered fields has been developed. Numerical results on scattered surface wave as well as bulk waves are given for different parameters of the incident beam. It is found that at low frequencies (ka≪1, where a is the grating period and k is the wave number in air), it is the inhomogeneity of the source that results in surface wave propagation in the scattered waves. The analysis is also applicable to impedance grating structures.