Comparison between an optical dielectric resonator nano-antenna reflectarray and an equivalent dielectric grating reflector

Conventional metallic nanoantennas suffer significant energy dissipation introduced by Drude metals in the optical frequency range. To overcome this limitation, optical dielectric resonator antenna (DRA) was proposed and demonstrated through a realization of optical DRA reflectarray with the capability of beam shaping. The reflectarray is composed of nanometer-scale cylindrical resonators operating in their fundamental HEM_11δ mode. Through a comparison with a volume-equivalent dielectric grating reflector, this paper demonstrates that the beam shaping cannot be achieved without the resonance mechanism with this small volume and height of dielectric material.