Phased-array nanophotonic systems are enabling the development new classes of refractive and diffractive optical elements.
In this article, we develop design principles for reconfigurable optical antennas and metasurfaces. We theoretically demonstrate the tunability of infrared scattering phase and radiation patterns in low-loss, high-index dielectric resonators using free carrier refraction. We demonstrate reconfigurable endfire antennas based on interference between multiple elements. Within single resonators, we demonstrate reconfigurable broadside antenna radiation lobes arising from interfering electric and magnetic dipole resonances. Extending this concept to infinite arrays, we design ideal Huygens metasurfaces with spectrally overlapping electric and magnetic dipole resonances. By introducing free charge carriers into these metasurfaces, we demonstrate continuously tunable transmission phase between 0 and 2π with less than 3 dB loss in intensity.
Such tunable metasurfaces may form the basis for reconfigurable metadevices that enable unprecedented electromagnetic field control.