A coding Janus metasurface is designed to generate four independent holographic images in both specifically polarized reflection and transmission channels under excitations of ypolarized incidence with the opposite propagation directions simultaneously. The proposed metasurface realizes the general functions of electromagnetic wave manipulation in full space. The full-space electromagnetic wave control is realized by introducing parametric variations and internal rotations in the multilayered elementary cell structure. Numerical calculations and experimental results obtained in the microwave domain verify the consistent performance of the multifunctional metasurface and provide a simple method for functional expansion of efficient devices.
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.
Hologram technology has attracted a great deal of interest in a wide range of optical fields owing to its potential use in future optical applications, such as holographic imaging and optical data storage. Although there have been considerable efforts to develop holographic technologies using conventional optics, critical issues still hinder their future development. A metasurface, as an emerging multifunctional device, can manipulate the phase, magnitude, polarization and resonance properties of electromagnetic fields within a sub-wavelength scale, opening up an alternative for a compact holographic structure and high imaging quality. In this review paper, we first introduce the development history of holographic imaging and metasurfaces, and demonstrate some applications of metasurface holography in the field of optics. We then summarize the latest developments in holographic imaging in the microwave regime. These functionalities include phase- and amplitude-based design, polarization multiplexing, wavelength multiplexing, spatial asymmetric propagation, and a reconfigurable mechanism. Finally, we conclude briefly on this rapidly developing research field and present some outlooks for the near future.
Multiplexing technologies can be used as a platform for low-cost, high-performance, and large-capacity holographic displays and data storage systems. In this paper, a polarization multiplexed method is proposed to realize two different information channels under orthogonally linear-polarized incidences utilizing the coding metasurface. Based on the modified weighted Gerchberg–Saxton (GSW) algorithm, a two-bit coding metasurface is designed with a set of double-layer cross-type meta-atoms to encode the holographic phase information, which can reflect two independent holographic images with respect to different incident polarization. The experimental results agree well with the numerical simulations and the theoretical predictions, which make the proposed multiplexed two-bit coding meta-hologram a great potential in numerous applications such as data storage and information processing.
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