Nonlinear metasurfaces provide a promising platform for integrated nonlinear photonic devices owing to their unprecedented capability of nonlinear wavefront manipulation. However, the previously reported second-harmonic (SH) metasurfaces are mainly based on the nonlinear Pancharatnam–Berry phase modulation. While this method is quite convenient and robust, it shows limitations of modulation efficiency and the difficulty in extending to multidimensional combined modulations. Here, the resonant nonlinear synthetic metasurface is proposed and experimentally demonstrated for independent phase and amplitude modulations of the SH beam. A high SH modulation efficiency of 75% (with a theoretical limit of 90%) is achieved in the polarization-dependent SH metalens. Moreover, SH holographic imaging with phase and amplitude (at 2 and 4 levels) combined modulation is realized experimentally. Compared with the pure-phase modulation, the signal-to-noise ratios are increased by 2 and 3 times when 2- and 4-level amplitude controls are introduced. This is not only an important step in the improvement and innovation of holographic display technology, but also paves a distinct avenue toward multifunctional, higher efficiency, and ultracompact nonlinear optical devices.

中文翻译：

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具有组合相位和幅度调制的谐振非线性合成超表面

非线性超表面由于其前所未有的非线性波前操纵能力，为集成非线性光子器件提供了一个有前途的平台。然而，先前报道的二次谐波 (SH) 超表面主要基于非线性 Pancharatnam-Berry 相位调制。虽然这种方法非常方便和稳健，但它显示出调制效率的局限性，并且难以扩展到多维组合调制。在这里，提出了谐振非线性合成超表面，并通过实验证明了 SH 光束的独立相位和幅度调制。在偏振相关的 SH 超透镜中实现了 75% 的高 SH 调制效率（理论极限为 90%）。而且，通过实验实现了相位和幅度（在 2 和 4 级）组合调制的 SH 全息成像。与纯相位调制相比，引入2级和4级幅度控制后，信噪比提高了2倍和3倍。这不仅是全息显示技术改进和创新的重要一步，而且为多功能、更高效率和超紧凑非线性光学器件开辟了一条独特的道路。