Polarization is the nature of optics. Exploiting metasurface's polarizations can enhance the multiplexing capacity but face a limited number of channels. For example, a single‐layer metasurface can offer three independent channels with six degrees of freedom (DoFs) including the amplitude and phase of Ex, Exy(yx), and Ey of the Jones matrix. In this work, it is theoretically demonstrated that the degrees of freedom of dual‐layer metasurfaces can reach eight, overcoming the polarization multiplexing constraints of single‐layer metasurfaces and that the cross‐talk can be largely reduced as compared with single‐layer metasurfaces when the channel number is larger than three. Numerical calculations manifest a decrease of 100%, 63%, and 50% for the cross‐talk of channels 4, 5, and 6, respectively. As a proof‐of‐concept demonstration of high‐capacity polarization multiplexing, an arbitrary‐polarization‐controlled 5‐channel dual‐layer metasurface exhibiting five nanoprintings and five holographic images with reduced cross‐talk under different incident and output polarizations is successfully designed. Thus, the research highlighting the high‐multiplexing‐capacity of dual‐layer metasurfaces can significantly advance multifunctional optical devices with high efficiency, simple integration, and ease of manipulation.

中文翻译：

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双层超表面增强偏振复用能力

偏振是光学的本质。利用超表面的偏振可以增强复用容量，但面临通道数量有限的问题。例如，单层超表面可以提供具有六个自由度（DoF）的三个独立通道，包括振幅和相位乙X,乙坐标（坐标）， 和乙y琼斯矩阵。本文从理论上证明了双层超表面的自由度可以达到8个，克服了单层超表面的偏振复用约束，并且与单层超表面相比，串扰可以大大减少。通道数大于3。数值计算表明通道 4、5 和 6 的串扰分别降低了 100%、63% 和 50%。作为高容量偏振复用的概念验证演示，成功设计了一种任意偏振控制的 5 通道双层超表面，该超表面具有 5 个纳米印刷和 5 个全息图像，并且在不同入射和输出偏振下串扰减少。因此，强调双层超表面的高复用能力的研究可以显着推进高效、简单集成和易于操作的多功能光学器件。