Electrically Reconfigurable Metasurfaces Using Heterojunction Resonators

An electrically reconfigurable metasurface comprising an array of 1D semiconductor Mie resonators on a reflecting ground plane is theoretically demonstrated. The design is based on magnetic dipole modes that interfere with image fields in a metal substrate to produce a 2π phase shift in reflection about the resonance wavelength. Analogous voltage-dependent phase shifts are produced using novel InSb/In0.8Al0.2Sb heterojunction resonators incorporating top electrodes that minimize perturbations of the electromagnetic mode. The devices exploit large swings in the InSb electron density to produce mid-infrared resonances tunable through free carrier refraction. Combined electrical device and full wave electromagnetic simulations show up to 300° phase shifts with less than 1dB of loss. Using this resonator as a basic building block, an electrically tunable metasurface is demonstrated. By applying a voltage gradient across the metasurface, an incident beam is steered in a unidirectional fashion continuously between ±72° (from normal incidence. This work describes a pathway to unprecedented control of light via electrically reconfigurable metasurfaces.