Ultra-thin and high-efficiency graphene metasurface for tunable terahertz wave manipulation

We propose a type of ultra-thin metasurfaces composed of rectangular graphene patches supporting orthogonal plasmonic resonances, which can work in transmission or reflection modes for dynamic terahertz wavefront manipulation with high polarization conversion ratio. By controlling the response of each patch via electrical biasing, the phase of the output wave can be tuned in a wide range over 180° while keeping its amplitude high and relatively stable. We demonstrate several functional devices based on such metasurfaces: a linear polarization converter with nearly 100% polarization conversion ratio, a switchable anomalous wave deflection device, and a dual-polarity focusing mirror with the focal spot tunable in both the transversal and longitudinal directions.