Programmable anisotropic digital metasurface for independent manipulation of dual-polarized THz waves based on voltage-controlled phase transition of VO2 microwires.

Programmable metasurfaces incorporated with tunable materials controlled by external stimuli can provide an unprecedented degree of freedom in dynamical wave manipulation in real-time. Beyond the scope of isotropic reconfigurable metasurfaces that only support unique tunable responses for excitation with a certain single-polarization, here, for the first time a new generation of ultrafast reprogrammable multi-functional anisotropic metasurface is reported to enable interchangeable missions independently for two orthogonal linearly polarized THz wavefront excitations. The reconfigurability of the proposed anisotropic meta-device was guaranteed by elaborately designed meta-particle composed of two perpendicular VO2 microwires whose operational statuses can be arbitrarily and dynamically tuned among two digital states of 0 and 1 independent for dual-polarization channels by mere changing the biasing voltage via two independent computer-programmed multichannel DC network. Capitalizing on such meta-particle design, single/multiple focused THz beam into a pre-determined focal spot and single/multiple focused vortex beams with interchangeable OAM modes satisfactorily generated by encoding a metasurface with different parabola and spiral-parabola-like coding sequences respectively. Besides controlling the near field behaviors, the versatility and flexibility of the proposed anisotropic metasurface also can furnish an inspiring platform to manipulate the far-field scattering patterns in each desired polarization channel. Anisotropic meta-device bringing new degrees of freedom in achieving versatile tunable control of differently polarized electromagnetic waves which will significantly enhance storage density and data capacities and has the potential for complicated wave manipulation such as ultrafast THz communication and dynamic holography.