An Efficient Method for Light Beaming from Subwavelength Slits Surrounded by Surface Gratings

Abstract

This paper investigates the directional beaming of metallic subwavelength slits surrounded by dielectric gratings. The design of the structure for light beaming was formulated as an optimization problem for the far-field angular transmission. A vertical mode expansion method was developed to solve the diffraction problem, which was then integrated into a genetic algorithm and an active set method to obtain the optimal result. By using the proposed method for a two-slit structure, we demonstrate that both the single- and dual-beaming effects can be efficiently achieved. Moreover, the beaming directions can be flexibly adjusted and precisely controlled.