Abstract
Abstract Owing to the potential to manipulate simultaneously amplitude and phase of electromagnetic wave, complex-amplitude holographic metasurfaces (CAHMs) can achieve improved image-reconstruction quality compared with amplitude-only and phase-only ones. However, prevailing design methods based on Huygens–Fresnel theory for CAHMs, e.g., Rayleigh–Sommerfeld diffraction theory (RSDT), restrict acquisition of high-precision reconstruction in a large field of view (FOV), especially in the small numerical aperture (NA) scenario. To this end, a CAHM consisting of Sine-shaped meta-atoms is proposed in a microwave region, enabled by a novel complex amplitude retrieval method, to realize large FOV holograms while breaking the large NA limitation. Calculations and full-wave simulations demonstrate that the proposed method can achieve superior-quality holograms, even for nonparaxial holograms in a relatively small NA scenario, thus improving FOV and aperture utilization efficiency of CAHMs. The reconstruction comparison of a complex multi-intensity field distribution between CAHM prototypes designed by our method and by RSDT further confirms this point. We also compare both theoretically and experimentally the CAHM by our method with the phase-only metasurface by weighted Gerchberg–Saxton algorithm. Superior-quality holograms with suppressed background noise and relieved deformation, promised by the extra amplitude manipulation freedom, is witnessed. Finally, due to its wavelength irrelevance, the proposed method is applicable to the entire spectrum, spanning from microwave to optics.
Highlights
Metasurfaces, a two-dimensional modality of metamaterials, have received extensive attention owing to their extraordinary capabilities to control amplitude, phase, and polarization of electromagnetic waves flexibly [1–27]
Prevailing design methods based on Huygens– Fresnel theory for complex-amplitude holographic metasurfaces (CAHMs), e.g., Rayleigh–Sommerfeld diffraction theory (RSDT), restrict acquisition of highprecision reconstruction in a large field of view (FOV), especially in the small numerical aperture (NA) scenario
A CAHM consisting of Sine-shaped meta-atoms is proposed in a microwave region, enabled by a novel complex amplitude retrieval method, to realize large FOV holograms while breaking the large NA limitation
Summary
Metasurfaces, a two-dimensional modality of metamaterials, have received extensive attention owing to their extraordinary capabilities to control amplitude, phase, and polarization of electromagnetic waves flexibly [1–27]. Due to the additional degree of freedom in controlling the wave fronts, the complex-amplitude hologram metasurface (CAHM) is expected to exhibit superior imaging quality beyond PHM and AHM. Such a perception has not yet been theoretically or experimentally demonstrated since the available synthesis methods for the CAHM fail to fulfill completely their potentials. The most widely used methods to synthesize CAHMs are based on the Huygens–Fresnel theory, e.g., Rayleigh–Sommerfeld diffraction theory (RSDT) It discretizes target fields as a limited number of point sources and calculates the diffraction fields of every point source by the RSDT, which are further superimposed in space to obtain amplitude and phase profiles in the hologram plane. Full-wave simulations and experiments are completed to verify the superiority of our CGSW and the corresponding CAHM, compared with the RSDT and the GSW
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