Analysis and Design of Vector Holographic Metasurfaces

In this work we present a comprehensive framework for the analysis and design of vector holographic metasurfaces (VHMS). The term vector refers to the metasurface ability to manipulate the polarization of the scattered wave, while holographic refers to the configuration of the metasurface aperture, which can have any arbitrary complex profile in its equivalent surface impedance (phase and/or magnitude). We start from the presentation of the analysis of such VHMS, i.e., the calculation of its scattering under given equivalent surface impedance configuration and illumination; the analysis relies on physical optics and can, in theory, model the scattering and diffraction by a finite-aperture metasurface of arbitrary convex shape under arbitrary spatially coherent wavefront illumination. We then present the VHMS design and synthesis procedure, i.e., we compute its equivalent and physical configuration, when given the illuminating wavefront and the desired scattering response or functionality, e.g., beam steering or focusing. For the synthesis, we use a simple scalable unit cell topology incorporating square conductor patches interconnected with lumped complex loads; these can locally and continuously tune the VHMS phase and amplitude response, with independent control over both polarizations, thus allowing arbitrary incident-to-scattered wavefront transformations. These versatile devices, especially when fused with wavefront sensing capabilities, can be used in applications spanning wireless communications (e.g., beamforming, integrated/joint sensing and communication, or programmable wireless environments), radar scattering (e.g., stealth), and holography/imaging.