Fields and currents due to a modulated laser beam exciting an array of narrow slots

Abstract

A properly modulated laser beam illuminating a conducting surface causes electrons to be emitted in such a way that the resulting electromagnetic radiation is equivalent to that from a distribution of electric dipoles oriented normal to the surface and located on or near the surface. The distribution of these dipoles over the illuminated spot is dictated by the laser-light intensity distribution and their spatial oscillation is controlled by the laser modulation. If an appropriate modulation is used then oscillation will occur at a selected frequency /spl omega/. The distribution of dipoles, at an angular frequency /spl omega/, on the conducting surface over a region which is illuminated by a laser beam can be treated as an electromagnetic source in an analysis where one attempts to predict the fields and currents induced on and in the medium around the conducting surface. In this paper we present a study of the fields and currents induced on and around an array of narrow slots by a distribution of normally-directed electric dipoles on the surface of the conducting screen containing the slots. The distribution of electric dipoles serves as a model for the modulated laser beam. One can write the coupled integral equations for coupled slots using steps similar to those used for a single slot. After modifying the excitation the fields and currents are calculated by solving the coupled integral equations using the method of moments.