Programmable anisotropic digital metasurface for independent manipulation of dual-polarized THz waves based on a voltage-controlled phase transition of VO₂microwires

Abstract

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. Consequently, two/four arbitrary oriented pencil beams, twin vortex beams with opposite OAM modes and random diffusion of terahertz wave are also realized by the proposed structure. 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.

Towards intelligent reflecting surface empowered 6G terahertz communications: A survey

“…Then, the IRS can freely manipulate the propagation direction of THz beam by designing different arrangement of reflecting elements, including polarization state and wave front shape. As discussed before, the key problem of designing IRS is to optimize the dynamic sub-wavelength reflecting elements, and the popular control methods make full use of dynamic materials, such as are composed of VO 2 [174][175][176], liquid crystal [177][178][179], graphene [180] and so on. It is worth noting that the hardware structure of graphene-based IRS has been designed in [41], as shown in Figure 10.…”

Deep neural network-based automatic metasurface design with a wide frequency range

“…Metamaterials, defined as artificial media composed of engineered subwavelength periodic or nonperiodic geometric arrays, have witnessed significant attention due to their exotic properties capable of modifying the permittivity and permeability of materials 1 – 3 . Today, just two decades after the first implementation of metamaterials by Smith et al 4 who unearthed Veselago’s original paper 5 , metamaterials and their 2D counterpart, metasurfaces, have been widely used in practical applications such as, but not limited to, polarization conversion 6 , 7 , reconfigurable wave manipulation 8 , 9 , vortex generation 10 , 11 , and perfect absorption 12 , 13 . Programmable digital metamaterials remarkably provide a wider range of wave-matter applications which present them especially appealing in the usages of imaging 14 , smart metasurfaces 15 , 16 , information metamaterials 17 – 19 , and machine learning applications 20 , 21 .…”

A wide-angle and TE/TM polarization-insensitive terahertz metamaterial near-perfect absorber based on a multi-layer plasmonic structure

“…The introduction of tunable materials controlled by external stimuli provides programmable metasurfaces an unparalleled degree of freedom in dynamical wave manipulation in real-time. For example, novel ultrafast reprogrammable multi-functional anisotropic metasurface and ultrafast reprogrammable multi-mission bias encoded metasurface are realized based on Vanadium dioxide, which integrate multiple diversified functionalities into one single device 35,36 . And space-time digital metasurfaces can substantially expand the application scope of digital metamaterials, which realize the full manipulation of the power intensity pattern in a large space-time digital metasurface 37 .…”