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 2 pi 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 degrees 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 degrees (from normal incidence. This work describes a pathway to unprecedented control of light via electrically reconfigurable metasurfaces.