Spatial sorting and routing of electromagnetic waves based on polarization control

The polarization of a plane wave in free space is used to control the excitation and the directionality of a guided electromagnetic wave. Experiments are conducted using a two-dimensional waveguide made of two parallel aluminum plates which is externally excited. The upper plate, which has a linear array of holes, is externally illuminated by a polarized wave whose incident wavevector is contained within a plane perpendicular to the waveguide and containing the linear array. Surprisingly, measurements show that the propagation inside the waveguide is highly asymmetrical, and is controlled by the polarization of the incoming wave. This extraordinary phenomenon is explained in terms of a simple model involving a set of equivalent dipoles excited at the hole positions. This is a powerful tool to sort different polarizations of a free space beam to different propagation directions of guided electromagnetic waves.