近日，南京工业职业技术大学Xi Cao团队研究了基于布里渊区折叠的全介电超表面的角不敏感非线性增强。这一研究成果于2025年8月12日发表在《物理评论A》杂志上。

超表面已经成为加强光-物质相互作用的强大平台。最近的研究表明，支持高质量(Q)因子共振的全介质超表面，如连续介质（BIC）中的反极点模式和准束缚态，可以显著提高三次谐波产生（THG）效率。然而，一个关键的挑战仍然存在：精确控制这些共振的Q因子是困难的，并且在大入射角范围内保持高Q因子的要求更高。

研究组通过在超表面内引入微扰实现了THG的大幅增强。光线下的导模可以折叠到光锥中，从而产生高Q谐振模式。与以往的BIC相比，该折叠谐振在动量空间中表现出持久的高Q特性，使得实现角不敏感的非线性增强成为可能。所提出的超表面的角稳定性确保了始终如一的高非线性性能，使其成为非线性光学（如频率转换和光子信号处理）实际应用的可行候选者。

附：英文原文

Title: Angle-insensitive nonlinear enhancement in an all-dielectric metasurface via Brillouin-zone folding

Author: Siyu Fan, Yuqiang Wang, Xi Cao

Issue&Volume: 2025/08/12

Abstract: Metasurfaces have become a powerful platform for strengthening light-matter interactions. Recent research has shown that all-dielectric metasurfaces supporting high-quality (Q) factor resonances, such as anapole modes and quasibound states in the continuum (BIC), can significantly enhance third harmonic generation (THG) efficiency. Nevertheless, a key challenge remains: precisely controlling the Q factor of these resonances is difficult, and maintaining a high-Q factor across a wide range of incident angles is even more demanding. Here, we achieve substantial enhancement of THG by introducing perturbations within the metasurface. The guided modes below the light line can be folded into the light cone, resulting in high-Q resonant modes. Compared with previous BICs, this folded resonance exhibits a persistent high-Q characteristic in momentum space, which makes it possible to achieve angular insensitive nonlinear enhancement. The angular robustness of the proposed metasurface ensures consistent high nonlinear performance, making it a viable candidate for practical applications in nonlinear optics, such as frequency conversion and photonic signal processing.

DOI: 10.1103/gw9j-9dxk

Source: https://journals.aps.org/pra/abstract/10.1103/gw9j-9dxk