Nonlinear metasurfaces offer new paradigm for boosting optical effect beyond limitations of conventional materials. In this work, we present an alternative way to produce pronounced third-harmonic generation (THG) based on nonlinear field resonances rather than linear field enhancement, which is a typical strategy for achieving a strong nonlinear response. By designing and studying a nonlinear plasmonic-graphene metasurface at terahertz regime with hybrid-guided modes and bound states in the continuum modes, it is found that a THG with a narrow bandwidth can be observed, thanks to the strong resonance generated between a weak THG field and these modes. Such strong nonlinear field resonance greatly enhances the photon-photon interactions, thus resulting in a large effective nonlinear coefficient of the whole system. This finding provides new opportunity for studying nonlinear optical metasurfaces.

中文翻译：

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等离子体石墨烯超表面中非线性场共振引起的增强的三次谐波产生。

非线性超表面为增强光学效果提供了超越常规材料限制的新范式。在这项工作中，我们提出了一种基于非线性场共振而非线性场增强来产生明显的三次谐波产生（THG）的替代方法，这是实现强非线性响应的典型策略。通过设计和研究在太赫兹状态下具有混合引导模式和连续模式中的束缚态的非线性等离体-石墨烯超表面，发现由于弱THG之间产生的强共振，可以观察到带宽较窄的THG。字段和这些模式。这种强的非线性场共振极大地增强了光子-光子的相互作用，从而导致整个系统的有效非线性系数大。