Fu Peng, Pai Peng, Lan Wenze, Du Shuo, Shao Jiawei, Hu Leyong, Li Chensheng, Zhang Yuyang, Deng Zi-Lan, Liu Baoli, Yang Luyi, Gu Changzhi
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100190, China.
Nano Lett. 2025 Mar 12;25(10):3773-3780. doi: 10.1021/acs.nanolett.4c05599. Epub 2025 Mar 3.
Exceptional points (EPs) are unique features of non-Hermitian systems, where eigenvalues and eigenvectors coalesce, enabling functionalities such as ultrasensitive sensing and topological energy transfer. While higher-order EPs have been studied in microdisk cavities and circuits, their realization in metasurfaces has been challenging. In this work, we demonstrate the first realization of a third-order EP (EP3) in terahertz metasurfaces by tuning the near-field interaction between three gold split-ring resonators. This transition from second-order EP (EP2) to EP3 is validated by the simultaneous collapse of three eigenvalues and eigenfunctions. Using a global optimization algorithm combined with neural networks, we optimized the condition for EP3 in a high-dimensional parameter space. Our terahertz metasurface is suitable for ultrasensitive biosensing applications, offering a novel mechanism for EP3 realization and paving the way for advanced optical communication and sensing systems.
exceptional点（EPs）是非厄米系统的独特特征，在该系统中，本征值和本征向量合并，实现了诸如超灵敏传感和拓扑能量转移等功能。虽然高阶EPs已在微盘腔和电路中得到研究，但其在超表面中的实现一直具有挑战性。在这项工作中，我们通过调整三个金裂环谐振器之间的近场相互作用，首次在太赫兹超表面中实现了三阶exceptional点（EP3）。从二阶exceptional点（EP2）到EP3的这种转变通过三个本征值和本征函数的同时坍缩得到验证。使用结合神经网络的全局优化算法，我们在高维参数空间中优化了EP3的条件。我们的太赫兹超表面适用于超灵敏生物传感应用，为EP3的实现提供了一种新颖机制，并为先进的光通信和传感系统铺平了道路。
