Reconfigurable Semiconductor Phased-Array Metasurfaces

Phased-array metamaterial systems are enabling new classes of refractive and diffractive optical elements through spatial-phase engineering. 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 2 pi with less than 3 dB loss in intensity. Such tunable metasurfaces may form the basis for reconfigurable metadevices that enable unprecedented control over the electromagnetic wavefront.