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Metasurfaces have attracted broad interest thanks to their unprecedented capacity for electromagnetic wavefront manipulation. The compact, ultrathin and multifunctional metasurface calls for novel design principles. Here, we propose and experimentally demonstrate a non-interleaved and non-segmented bidirectional Janus metasurface that encodes multiple functionalities in full-space scattering channels with different propagation directions and polarization in the microwave region. Specifically, by rotating and adjusting the elementary double-arrow-shaped structure within the same meta-atom, the independent phase control can be achieved in both cross-polarized transmission and co-polarized reflection components under oppositely directed incident waves. Our metasurface with broken mirror symmetry can fully exploit four independent information channels under opposite propagation directions. A series of proof-of-concept is constructed to validity of our methodology, and the simulations and experimental results further show that the proposed non-interleaved bidirectional metasurface can provide an attractive platform for various applications, ranging from structured light conversion, optical imaging, multifunctional optical information processing and others.

In this paper, a novel method is proposed to achieve two distinct information channels by simultaneously manipulating both the transmitted cross- and co-polarized components of a 1-bit coding metasurface under linearly polarized incidence. Compared to previously demonstrated incidence-switchable or position multiplexed holograms, our proposed coding meta-hologram can simultaneously project two independent holographic images without inevitable change of the incidence state and can at the same time also avoid crosstalk between different channels. Moreover, the orientation of the double-layered split ring (SR) apertures is specially designed to be 45° or 135° to achieve identical multiplexed functionality for both x-polarized and y-polarized incidences. The proof-of-concept experimental demonstrations present total transmittance efficiency above 30% for the dual linearly polarized incidences at 15 GHz, and good imaging performances with 53.98%/48.18% imaging efficiency, 1.55%/1.46% RMSE, and 29.9/28.72 peak signal-to-noise ratio for the cross-/co-polarized channels under y-polarized incidence, and 47.27%/45.75% imaging efficiency, 1.55%/1.43% RMSE, and 18.74/25.93 peak signal-to-noise ratio under x-polarized incidence, demonstrating great potential of the proposed multiplexed coding meta-hologram in practical applications such as data storage and information processing.

In this paper, a 0.1λ0-thick 1-bit coding metasurface is proposed to achieve a polarization-insensitive hologram under oblique incidence, utilizing compact ground-backed patch unit cells. Fourier convolution theory in a digital signal processing system is added to the hologram calculation of the improved weighted Gerchberg–Saxton (GSW) algorithm to achieve control of the scattered pattern in the microwave region. As a proof of concept, a prototype operating at 15 GHz is designed to verify the validity of our proposed approach. The measured performances show good imaging quality under different incident polarizations, providing potential applications in imaging processing and information storage. [ABSTRACT FROM AUTHOR]

Metasurface holographic encryption, as an emerging and highly promising technique, presents the advantages of multi‐dimension and high security and consequently provides a flexible and convenient platform for information encryption. Recent years have witnessed rapid progress in meta‐holographic encryption through the utilization of different dimensions of electromagnetic (EM) waves, yet enhancing the capacity and security of encrypted information remains an endless goal. In this context, the concept of three physical dimensions encrypted metasurface holography is proposed in which orbital angular momentum (OAM) is fully synergized with frequency and polarization state. The mechanism relies on the simultaneous control of these dimensions and arbitrarily overlaying them in each operation channel, thereby acting as a multi‐dimensional key to realize information encryption and decryption. As a proof‐of‐concept experiment, a three‐physical dimension encrypted meta‐hologram is designed that conceals four real images as encrypted information in 32 information channels. Remarkably, a specific OAM order, frequency, and polarization state is required to decrypt the designed meta‐hologram. This work opens a new avenue for multi‐dimensional encrypted holography, which has broad application prospects for information security and data storage in the era of big data. [ABSTRACT FROM AUTHOR]