Reconfigurable Infrared Phased-Array Semiconductor Metasurfaces

The ability to engineer the scattering \textit{phase} of metamaterial constituents offers tremendous potential for constructing new classes of beam steering, shaping, and focusing technologies. Current methods for engineering phase rely on static geometry-based effects. In this talk we describe methods to \textit{dynamically} tune the scattering phase of infrared semiconductor nanoantennas. We fabricate spherical silicon and germanium nanoparticles via femtosecond laser ablation and demonstrate size-dependent multipolar resonances throughout the infrared frequency range. We experimentally demonstrate that the resonance frequencies shift with doping, according to simple Drude models of free-carrier refraction. Using a combination of theoretical and analytical calculations we show that dynamically tuning free-carrier concentration can enable reconfigurable optical antennas and metasurfaces. Such dynamic tuning will enable reconfigurable photonic devices based on optical antenna and metamaterial concepts.