Superdirective magnetic nanoantennas with effect of light steering: Theory and experiment

Abstract

We introduce a novel concept of superdirective nanoantennas based on the generation of higher-order optically-induced magnetic multipoles. Such an all-dielectric nanoantenna can be realized as an optically small spherical dielectric nanoparticle with a notch excited by a point source located in the notch. Proposed superdirectivity effect is not associated with high dissipative losses, because of the magnetic nature of the nanoantenna operation. For these dielectric nanoantennas we predict the effect of the beam steering at the nanoscale characterized by a subwavelength sensitivity of the beam radiation direction to the source position. We confirm the predicted effects experimentally through scaling to the microwave frequency range.