No abstract

Digital coding metasurface, which provides a new approach to link the physical world and information science, has been quickly developed in recent years. However, all previously reported metasurfaces cannot achieve independent controls of different polarizations in both transmission and reflection spaces at the same time. In this work, a reconfigurable anisotropic digital coding metasurface loaded with electronically controlled PIN diodes is proposed that can independently manipulate not only the near/far‐field pattern but also the transmission and reflection modes of the electromagnetic waves under different polarizations. As a validation example, a multifunctional holographic imaging metasurface is designed, fabricated, and measured. Both simulated and measured results show that orthogonally polarized waves (vertical and horizontal polarizations) can be manipulated to achieve different images, and the transmission and reflection modes of the differently‐polarized images can be independently controlled in real time by changing the state of the loaded PIN diodes.

A thin metasurface has shown powerful capabilities in controlling either incident electromagnetic (EM) waves or radiation waves, but is difficult for both. Here, a self-feeding Janus metasurface (SFJ-MS) is proposed to manipulate the incident EM waves and emit the radiated waves simultaneously, which can realize the polarization conversion of incident waves, scattering control, EM wave radiation, and radiation-beam steering. On the upper of SFJ-MS, a diagonal-split square ring and a rectangular patch with rotation for radiation are designed to introduce anisotropy in the meta-atom for converting the polarization of incident EM waves. On the bottom of SFJ-MS, a self-feeding microstructure converts the alternating current into the excitation of SFJ-MS to emit the EM waves to free space. The multiple functions of SFJ-MS are comprehensively substantiated by measured results, which are in agreements with the stringent simulations. This SFJ-MS, with lightweight, compact, low profile, and power-efficient features, can find potential applications in phased array radar systems, wireless communication systems, polarimetric radar imaging systems, and target detection systems.

conductors (PECs) instead of plasmas with negative permittivity. In order to realize similar SPPs at low frequencies, the concept of spoof surface plasmon polaritons (SSPPs) was proposed since 2004 by decorating a series of 3D periodically artificial structures on the metal surface. [2][3][4][5][6] To overcome the complexity of 3D structures, an ultrathin corrugated metallic strip was proposed in 2013 to support and guide the SSPPs with high confinement even when it was bent, twisted, or wrapped arbitrarily. [7] To integrate such a single-conductor SSPP transmission line with the conventional two-conductor microwave transmission lines efficiently, some matching transitions were proposed to make a smooth conversion between the SSPP modes and traditional guided-wave modes. [8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.Recently, programmable metamaterials and metasurfaces have been developed greatly for the dynamic manipulation of electromagnetic (EM) waves, which give the possibility for a single device to possess different functionalities that can be electrically switched through field programming. [21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones. For example, by placing the split-ring resonators (SRRs) close to the plasmonic waveguide, the resonance of the SRR will introduce a narrow rejection band, whose central frequency can be tuned by controlling the resonant response of the SRRs. [15,16,31] However, these designs usually suffer from the shortcomings of narrow rejection band and poor stability due to the strong resonance of the SRRs. Recently, the concepts of programmable SSPPs to realize three digital-analog functionalities, [36] reconfigurable SSPPs to realize frequency spectrum tunable SSPPs filter, [37] and tunable spoof surface plasmon transmission line (SSP-TL) to construct a compact and frequency-reconfigurable Wilkinson power divider [38] have been proposed one after another. However, they can only control the fundamental mode of SSPPs.Spoof surface plasmon polaritons (SSPPs) can be supported and propagated on metal surfaces decorated with periodic subwavelength structures, whose dispersion properties are determined by geometrical dimensions of unit structures. However, the functions of plasmonic devices made of the conventional passive SSPPs will be fixed once the devices are fabricated. Here, an electronically controlled programmable SSPP waveguide is presented, whose dispersions can be manipulated in real time at fast speed by programing the bias voltage instead of changing the dimensions of the unit structures. There are three different modes at different frequency bands, with a forbidden band existing between the...

A class of anisotropic, transmissive electromagnetic metasurfaces is presented, which enable independent and simultaneous control of copolarized phase and amplitude responses to two linear, orthogonal polarizations. By varying the geometrical parameters, the transmission response of the proposed structure can yield a full phase coverage, accompanied by broadly adjustable amplitude and negligible cross‐polarized components. The full amplitude‐phase control together with the novel anisotropic character allows efficient implementation of complicated field manipulations. As representative application examples, which cannot be realized via conventional (phase‐only) metasurfaces, it is presented here: (1) the radiation of multiple equal‐power vortex beams (along arbitrarily predesigned directions, with designable orbital angular momentum modes under different polarizations), and (2) the realization of polarization‐reconfigurable multifocal metalenses. Full‐wave numerical simulations and experimental results demonstrate good agreement and confirm the versatility and effectiveness of the proposed approach to design advanced field‐manipulation systems.