Nonlinear absorption is a significant topic in classic nonlinear sciences. Today, a growing interest in this area is drawn by increasingly severe interferences associated with strong microwaves. Although conventional absorbers may help mitigate the harmful effects, they unavoidably cause a huge loss to small useful signals. Here, a novel nonlinear absorbing metasurface is proposed targeting spatial waves. Based on an active nonlinear mechanism, the input impedance of the metasurface is highly dependent on the wave intensity. When the waves get stronger, the impedance-match between the meta-surface and free space is improved, so they are preferably allowed to enter the structure and be dissipated inside. A prototype is fabricated and measured in a microwave anechoic chamber, and its intriguing characteristics such as wide incident angle scope, dual polarizations, and wide instantaneous bandwidth are demonstrated, which are in good agreement with theoretical and simulated anticipations. With an ultralow profile and a simple direct-current-supplying strategy, the proposal can find potential applications in various scenarios to reinforce the protection of the weak against the strong.

中文翻译：

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用于空间波吸收的高性能非线性超表面

非线性吸收是经典非线性科学中的一个重要课题。今天，与强微波相关的日益严重的干扰引起了人们对这一领域的日益浓厚的兴趣。尽管传统的吸收器可能有助于减轻有害影响，但它们不可避免地会对小的有用信号造成巨大损失。在这里，提出了一种针对空间波的新型非线性吸收超表面。基于主动非线性机制，超表面的输入阻抗高度依赖于波强度。当波变强时，超表面和自由空间之间的阻抗匹配得到改善，因此最好允许它们进入结构并在内部消散。在微波消声室中制造和测量原型，以及其有趣的特性，如宽入射角范围、证明了双极化和宽瞬时带宽，这与理论和模拟预期非常吻合。凭借超低的外形和简单的直流供电策略，该提案可以在各种场景中找到潜在的应用，以加强对强者的保护。