On the use of a Gaussian beam to isolate the edge scattering from a plate of finite size

Free-space focused beam measurement systems are sometimes used to illuminate an edge of a sample under investigation while observing the scattering response. Typically, these kinds of measurements are performed to try to categorize the scattering from an edge of a material. Therefore, in this paper, a study is performed to obtain guidelines for the conditions under which the scattering of the beam is almost completely determined by the illuminated edge; that is, there is negligible scattering due to other physical structure immediately outside of the spot of the beam. The guidelines are obtained by comparing edge scattering due to a Gaussian beam incident on an infinitesimally thin, perfectly conducting plate with the edge scattering due to the same beam incident on an infinitesimally thin, perfectly conducting half-plane. The half-plane can be viewed as the ideal object for studying edge scattering because it contains only one edge. So the comparison between the plate and the half-plane determines the effect of the additional edges of the plate on the scattered field.