Diffraction of a Gaussian beam from a periodic planar screen

Abstract

The diffraction of electromagnetic radiation from one-dimensional planar transmittive screens illuminated by Gaussian-profile beams is examined. The incident Gaussian beam is expressed as a superposition of elementary plane waves that propagate along different directions, with the aid of the plane-wave spectrum technique based on Fourier optics. For each elementary plane wave, the diffracted field is obtained by applying the spectral domain method combined with the method of moments. Results for the cases of normal and oblique incidence are in agreement with theoretically expected properties of such planar screens and are found to be very sensitive to the aspect ratio γ (strip width to period). The diffracted beam is composed of distinct subbeams that propagate along specific directions. These directions coincide with the Floquet harmonics generated by an incident plane wave propagating along the same direction as the initial beam.