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Holography based on optical metasurfaces has attracted a steadily increasing interest. However, most of the optical metasurfaces usually suffer from limited number and fixed viewing angles of multiplexed holography images in one channel. Here, by modifying the Gerchberg–Saxton algorithm, a multiplexed holography at arbitrary‐planes is proposed at two arbitrary microwave frequency bands. As a proof‐of‐concept demonstration, two independent information channels can be established by a single metasurface through dual‐frequency meta‐atoms. The metasurface composed of 35 × 35 meta‐atoms can simultaneously produce four images with 45° and 60° viewing angles at 10 GHz and five images with vertical and horizontal viewing angles at 16 GHz. The experimental results verify the design concept, making it possible to generate multiplexed holography in arbitrary‐planes, and allowing multiplexed functionalities in a variety of applications such as microscopy, display, security, data storage, and information processing. [ABSTRACT FROM AUTHOR]

Zoom lenses with variable focal lengths and magnification ratios are essential for many optical imaging applications. Conventional zoom lenses are composed of multiple refractive optics, and optical zoom is attained via translational motion of one or more lens elements, which adds to module size, complexity, and cost. In this paper, a zoom lens design based on multi‐functional optical metasurfaces is presented, which achieves large step zoom ratios, minimal distortion, and diffraction‐limited optical quality without requiring mechanical moving parts. Two embodiments of the concept are experimentally demonstrated based on polarization‐multiplexing in the visible and phase change materials in the mid‐infrared, both yielding 10× parfocal zoom in accordance with the design. [ABSTRACT FROM AUTHOR]

Metasurfaces have provided a novel and promising platform for realizing compact and high‐performance optical devices. The conventional metasurface design approach assumes periodic boundary conditions for each element, which is inaccurate in most cases since near‐field coupling effects between elements will change when the element is surrounded by nonidentical structures. In this paper, a deep learning approach is proposed to predict the actual electromagnetic (EM) responses of each target meta‐atom placed in a large array with near‐field coupling effects taken into account. The predicting neural network takes the physical specifications of the target meta‐atom and its neighbors as input, and calculates its actual phase and amplitude in milliseconds. This approach can be used to optimize metasurfaces' efficiencies when combined with optimization algorithms. To demonstrate the efficacy of this methodology, large improvements in efficiency for a beam deflector and a metalens over the conventional design approach are obtained. Moreover, it is shown that the correlations between a metasurface's performance and its design errors caused by mutual coupling are not bound to certain specifications (materials, shapes, etc.). As such, it is envisioned that this approach can be readily applied to explore the mutual coupling effects and improve the performance of various metasurface designs. [ABSTRACT FROM AUTHOR]

Metasurfaces have enabled precise electromagnetic (EM) wave manipulation with strong potential to obtain unprecedented functionalities and multifunctional behavior in flat optical devices. These advantages in precision and functionality come at the cost of tremendous difficulty in finding individual meta‐atom structures based on specific requirements (commonly formulated in terms of EM responses), which makes the design of multifunctional metasurfaces a key challenge in this field. In this paper, a generative adversarial network that can tackle this problem and generate meta‐atom/metasurface designs to meet multifunctional design goals is presented. Unlike conventional trial‐and‐error or iterative optimization design methods, this new methodology produces on‐demand free‐form structures involving only a single design iteration. More importantly, the network structure and the robust training process are independent of the complexity of design objectives, making this approach ideal for multifunctional device design. Additionally, the ability of the network to generate distinct classes of structures with similar EM responses but different physical features can provide added latitude to accommodate other considerations such as fabrication constraints and tolerances. The network's ability to produce a variety of multifunctional metasurface designs is demonstrated by presenting a bifocal metalens, a polarization‐multiplexed beam deflector, a polarization‐multiplexed metalens, and a polarization‐independent metalens. [ABSTRACT FROM AUTHOR]

In this letter, a simple metasurface superstrate structure is proposed to reduce mutual coupling of both E-plane and H-plane coupled patch antennas. The proposed metasurface consists of periodic ring slots arranged on one side of the substrate. The metasurface can suppress the surface wave and partly change the coupling mode, which can achieve isolation enhancement of more than 40 dB at resonant frequency in both E/H-plane coupled patch antennas. The edge-to-edge spacing between antenna elements is 2 mm (0.023 λ0). The prototypes of E-plane and H-plane arrays with metasurfaces are fabricated, and the experimental measurements and the simulation results are in good agreement. [ABSTRACT FROM AUTHOR]