Liu Yulian, Zhu Shan, Zhou Qingjia, Cao Yanyan, Fu Yangyang, Gao Lei, Chen Huanyang, Xu Yadong
Opt Express. 2020 Apr 27;28(9):13234-13242. doi: 10.1364/OE.391294.
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.
非线性超表面为突破传统材料的限制来增强光学效应提供了新的范式。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显著的三次谐波产生（THG）的替代方法，线性场增强是实现强非线性响应的典型策略。通过设计和研究处于太赫兹波段的具有混合导模和连续谱束缚态的非线性等离子体 - 石墨烯超表面，发现由于弱THG场与这些模式之间产生的强共振，可以观察到具有窄带宽的THG。这种强非线性场共振极大地增强了光子 - 光子相互作用，从而导致整个系统具有大的有效非线性系数。这一发现为研究非线性光学超表面提供了新的机会。
