Yang Zijin, Huang Po-Sheng, Lin Yu-Tsung, Qin Haoye, Zúñiga-Pérez Jesús, Shi Yuzhi, Wang Zhanshan, Cheng Xinbin, Tang Man-Chung, Han Sanyang, Kanté Boubacar, Li Bo, Wu Pin Chieh, Genevet Patrice, Song Qinghua
Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China.
School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
Nat Commun. 2024 Jan 4;15(1):232. doi: 10.1038/s41467-023-44428-z.
Exceptional points (EPs) can achieve intriguing asymmetric control in non-Hermitian systems due to the degeneracy of eigenstates. Here, we present a general method that extends this specific asymmetric response of EP photonic systems to address any arbitrary fully-polarized light. By rotating the meta-structures at EP, Pancharatnam-Berry (PB) phase can be exclusively encoded on one of the circular polarization-conversion channels. To address any arbitrary wavefront, we superpose the optical signals originating from two orthogonally polarized -yet degenerate- EP eigenmodes. The construction of such orthogonal EP eigenstates pairs is achieved by applying mirror-symmetry to the nanostructure geometry flipping thereby the EP eigenmode handedness from left to right circular polarization. Non-Hermitian reflective PB metasurfaces designed using such EP superposition enable arbitrary, yet unidirectional, vectorial wavefront shaping devices. Our results open new avenues for topological wave control and illustrate the capabilities of topological photonics to distinctively operate on arbitrary polarization-state with enhanced performances.
由于本征态的简并性，奇异点（EPs）能够在非厄米系统中实现引人入胜的非对称控制。在此，我们提出一种通用方法，该方法扩展了EP光子系统的这种特定非对称响应，以处理任意全偏振光。通过在EP处旋转超结构，可以将潘查拉特纳姆 - 贝里（PB）相位专门编码在其中一个圆偏振转换通道上。为了处理任意波前，我们叠加源自两个正交偏振但简并的EP本征模的光信号。通过对纳米结构几何形状进行镜像对称翻转，从而使EP本征模的手性从左旋圆偏振变为右旋圆偏振，实现了这种正交EP本征态对的构建。使用这种EP叠加设计的非厄米反射PB超表面能够实现任意但单向的矢量波前整形器件。我们的结果为拓扑波控制开辟了新途径，并展示了拓扑光子学在以增强性能对任意偏振态进行独特操作方面的能力。
