Chen Yang, Chen Weijin, Kong Xianghong, Wu Dong, Chu Jiaru, Qiu Cheng-Wei
Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, 230027 Hefei, China.
Department of Electrical and Computer Engineering, National University of Singapore, 117583 Singapore, Singapore.
Phys Rev Lett. 2022 Apr 8;128(14):146102. doi: 10.1103/PhysRevLett.128.146102.
Strong coupling between resonant states is usually achieved by modulating intrinsic parameters of optical systems, e.g., the refractive index of constituent materials or structural geometries. Externally introduced chiral enantiomers may couple resonances, but the extremely weak chirality of natural enantiomers largely prevents the system from reaching strong coupling regimes. Whether weak chirality could induce strong coupling between resonant states remains an open question. Here, we realize strong coupling between quasibound states in the continuum of a high-Q metasurface, assisted with externally introduced enantiomers of weak chirality. We establish a chirality-involved Hamiltonian to quantitatively describe the correlation between the coupling strength and the chirality of such systems, which provides an insightful recipe for enhancing the coupling of resonant states further in the presence of quite weak chirality. Consequently, high-sensitivity chiral sensing is demonstrated, in which the circular dichroism signal is enhanced 3 orders higher than the case without strong coupling. Our findings present a distinct strategy for manipulating optical coupling between resonances, revealing opportunities in chiral sensing, topological photonics, and quantum optics.
共振态之间的强耦合通常通过调制光学系统的固有参数来实现，例如组成材料的折射率或结构几何形状。外部引入的手性对映体可能会耦合共振，但天然对映体极弱的手性在很大程度上阻碍了系统达到强耦合状态。弱手性是否能诱导共振态之间的强耦合仍然是一个悬而未决的问题。在此，我们在具有弱手性的外部引入对映体的辅助下，实现了高Q值超表面连续体中准束缚态之间的强耦合。我们建立了一个涉及手性的哈密顿量，以定量描述此类系统的耦合强度与手性之间的相关性，这为在相当弱的手性存在下进一步增强共振态的耦合提供了深刻的方法。因此，展示了高灵敏度手性传感，其中圆二色性信号比没有强耦合的情况增强了3个数量级。我们的发现提出了一种操纵共振之间光学耦合的独特策略，揭示了在手性传感、拓扑光子学和量子光学方面的机会。
