Dielectric Resonator Nanoantennas: A Review of the Theoretical Background, Design Examples, Prospects, and Challenges

Dielectric resonator antennas (DRAs) represent a wellestabl ished concept for microwave frequencies. In recent years, DRAs and related counterparts have been embraced as structures for higher frequencies, including visible optics. This research trend is facilitated by advances in nanofabrication techniques and motivated by two prominent advantages of DRAs: 1) DRAs are highly efficient because their operation is based on displacement currents in low-loss dielectrics, and 2) DRAs are versatile radiating elements that can support multiple resonance modes when made of medium- or highpermittivity materials. In this article, we review our recent work on optical DRAs for high-efficiency beam control and reconfigurability. This review includes theoretical background and design examples as well as prospects and challenges of optical DRAs that we hope will be of interest to a broad audience in the antenna community.