An optical reflectarray nanoantenna: the concept and design.

This paper presents the concept and design of a reflectarray nanoantenna at optical frequencies whose elements are nano-sized concentric spherical particles with the core made of ordinary dielectrics and the shell made of a plasmonic material. Modeling approaches based on finite difference time domain (FDTD) numerical method and dipole-modes scattering theory are used to characterize and tune the reflectarray design. A 6x6 elements reflectarray nanoantenna operating at wavelength 357.1nm with narrow beamwidth is presented, and its scanned radiation characteristics for 15 degrees and 30 degrees are demonstrated.