Arbitrary order exceptional point induced by photonic spin–orbit interaction in coupled resonators
Arbitrary order exceptional point induced by photonic spin–orbit interaction in coupled resonators
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DOI：
10.1038/s41467-019-08826-6
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发表时间：
2018-10
影响因子：
16.6
通讯作者：
Shubo Wang;B. Hou;B. Hou;Weixin Lu;Yuntian Chen;Zhao-qing Zhang;C. T. Chan
中科院分区：
文献类型：
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作者：
Shubo Wang;B. Hou;B. Hou;Weixin Lu;Yuntian Chen;Zhao-qing Zhang;C. T. Chan
非厄米系统的许多新性质都是在复能量面的异常点（本征值和本征向量合并的分支点）处或其附近发现的。特别是，高阶例外点可以导致对外部扰动超敏感的光学结构。在这里，我们表明，一个任意阶例外点可以实现在一个简单的系统，包括放置在波导附近的相同的谐振器。由波导模式介导的谐振器的任意两个手征偶极态之间的单向耦合导致例外点，该例外点受到导波的横向自旋动量锁定的保护，并且与谐振器的位置无关。在例外点的谐振器的各种解析响应函数的实验表现在微波政权。数值和解析证明了异常点附近的外部扰动的灵敏度的增强。
Many novel properties of non-Hermitian systems are found at or near the exceptional points—branch points of complex energy surfaces at which eigenvalues and eigenvectors coalesce. In particular, higher-order exceptional points can result in optical structures that are ultrasensitive to external perturbations. Here we show that an arbitrary order exceptional point can be achieved in a simple system consisting of identical resonators placed near a waveguide. Unidirectional coupling between any two chiral dipolar states of the resonators mediated by the waveguide mode leads to the exceptional point, which is protected by the transverse spin–momentum locking of the guided wave and is independent of the positions of the resonators. Various analytic response functions of the resonators at the exceptional points are experimentally manifested in the microwave regime. The enhancement of sensitivity to external perturbations near the exceptional point is also numerically and analytically demonstrated.