Angular Inhomogeneity in Dielectric Cylinders for Large-Angle Beam Steering and Metagrating Design

In this work, we propose the use of angular inhomogeneity in infinite dielectric wires (cylinders) to achieve light deflection at large angles, almost perpendicular to the direction of incidence. We first study an isolated wire with a circular cross section, featuring angular inhomogeneity in its permittivity. To solve numerically this problem, we employ the volume integral equation (VIE) method, previously developed for radial inhomogeneity, and extend it to support angular inhomogeneity. We show that, when a TE plane wave impinges normally on an azimuthally inhomogeneous cylinder, directional scattering takes place in the scattering pattern, at a specific rotation angle. The results of the VIE are fully verified by finite element simulations. Next, we change the shape of the cylindrical cross section from circular to elliptical and show that an enhanced scattering cross-section is achieved, which translates into an increased directionality of the scattered beam under an oblique direction. Finally, we design a metagrating consisting of a periodic arrangement of elliptical meta-atoms with azimuthal variation in their permittivity and show that substantial light bending is realized, almost perpendicular to the direction of incidence.