Considerable effort is devoted to research on reconfigurable beam focusing and optical cloaking in the basis of metamaterials/metasurfaces. However, it remains a great challenge to achieve multifunctional wavefront control on curved platforms, especially in the reflective case, which is of paramount importance in the emerging fields of active optics and stealth research. This study proposes a novel strategy to control the versatile reflective structured wavefront on a conformal platform by curving a flexible metasurface. This metasurface is fabricated in a high‐throughput manner by using ultra‐violet nano‐imprinting lithography (UV‐NIL), and its efficacy is verified through consistent simulated and experimental results. The conformal metasurface is designed to realize multifunctional performance by employing all‐metallic plasmonic structures based on the Pancharatnam‐Berry (PB) phase. A general theoretical scheme is also proposed for the projection of a curved surface onto a reference plane by a judicious compensation, combining the geometrical PB phase with curvature‐induced propagation phase. Moreover, as a proof‐of‐concept, curved metasurfaces with cylindrical shapes are experimentally characterized by their multifunctionalities in generating a beam spot with a continuously tunable focal length and reflecting plane waves used for camouflage, thereby confirming the feasibility and effectiveness of the proposed strategy.
Conventional lens technologies face great challenges in applications requiring large apertures and small f‐numbers, while a liquid crystal (LC) lens based on geometric phase is a potential solution. However, the challenge of manufacturing a large size LC flat lens with high efficiency and high phase gradient still remains. Here, an improved interferometric exposure system is proposed to acquire a large‐size vectorial optical field for photo‐alignment. Bifacial LC layers are applied to reduce the focal length while maintaining a large aperture, high diffraction efficiency, and light weight. LC layers are deposited on both sides of the substrate with the same vector system. Finally, a bifacial LC flat lens with a 10 cm diameter and 88.37% diffraction efficiency is fabricated by using optical elements smaller than 2 in., while the effective focal length is reduced from 91.5 cm to 46 cm comparing to the single side LC lens. This work demonstrates the great advantages of LC‐based flat lenses for flat optical systems with large aperture.
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