A numerical examination of the diffraction properties of profiled beam transmission through binary apertures and random phase screens using fresnel-kirchhoff diffraction theory

Abstract

Propagation of uniform and profiled electromagnetic beams through apertures with binary amplitude transmission and random phase distributions at the far field (Fraunhofer limit) is investigated, and simulation results based on two approaches, (a) using the Fresnel-Kirchhoff diffraction integral directly, and (b) using a split step propagation concept whereby the aperture or phase screen is placed at an arbitrary location along the propagation path, are applied separately and compared. Results for uniform, Gaussian and Bessel profile beams propagating through a variety of binary apertures are examined and compared with analytical predictions wherever feasible. A power spectrum density of the modified von Karman spectrum (MVKS) model is also used to describe a planar aperture as a random phase distribution. This approach is prompted by the problem of electromagnetic propagation through a turbulent medium. Simulation results are limited to the diffraction intensity calculation of the intensity in the far-field or Fraunhofer regime evaluated in the in the transverse (image) plane. Additional examples, including diffraction through thin sinusoidal amplitude grating and far-field diffraction following propagation through a random phase screen for profiled input beams are also presented. These results, derived serendipitously while examining turbulent propagation, provide insight into the mechanisms of diffraction through variable apertures, beam profiles and medium characteristics. It should therefore be of interest to the study in general of near-and far-field diffraction of electromagnetic waves taken as a whole.