近日，华中科技大学的陈林及其研究团队取得一项新进展。经过不懈努力，他们通过非厄米系统中的开放演化轨迹实现手性传递。相关研究成果已于2024年3月5日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队证明了无需闭合轨迹的耦合波导系统中的手性动力学。具体而言，研究人员探索了一个开放轨迹，连接两个具有相同渐近本征模式的无限点(不是PT对称和反PT对称系统中的模式)，证明该平台能够实现高效的手性转移，每个本征模式都定位在单个波导中。这一概念在通信波长的耦合硅波导系统中进行了实验实现。这项研究工作为性能优越的手性动力学提供了一种新的演化策略，为开发实用的手性转移装置奠定了基础。

据悉，奇异点(EPs)是谐振系统的两个或多个本征值和本征态合并的点，它与具有增益和/或损耗元素的非厄米哈密顿量相关联。近年来，EPs的动态环绕引起了人们的极大兴趣，因为它已被证明会导致高度重要的现象，例如手性转移，其中系统的最终状态取决于环绕的手性。以前，通过在宇称-时间(PT-)或反PT-对称系统中建立一个封闭的动力学轨迹来实现一对本征模的手性转移。虽然通过在反PT对称系统中建立环绕EPs的闭合轨迹，已经实现了在实际光子集成电路中更容易实现的对称破缺模式的手性转移，但由于路径相关损耗，所证明的转移效率非常低。

附：英文原文

Title: Chiral transmission by an open evolution trajectory in a non-Hermitian system

Author: Shu, Xiaoqian, Zhong, Qi, Hong, Kai, You, Oubo, Wang, Jian, Hu, Guangwei, Al, Andrea, Zhang, Shuang, Christodoulides, Demetrios N., Chen, Lin

Issue&Volume: 2024-03-05

Abstract: Exceptional points (EPs), at which two or more eigenvalues and eigenstates of a resonant system coalesce, are associated with non-Hermitian Hamiltonians with gain and/or loss elements. Dynamic encircling of EPs has received significant interest in recent years, as it has been shown to lead to highly nontrivial phenomena, such as chiral transmission in which the final state of the system depends on the encircling handedness. Previously, chiral transmission for a pair of eigenmodes has been realized by establishing a closed dynamical trajectory in parity-time- (PT-) or anti-PT-symmetric systems. Although chiral transmission of symmetry-broken modes, more accessible in practical photonic integrated circuits, has been realized by establishing a closed trajectory encircling EPs in anti-PT-symmetric systems, the demonstrated transmission efficiency is very low due to path-dependent losses. Here, we demonstrate chiral dynamics in a coupled waveguide system that does not require a closed trajectory. Specifically, we explore an open trajectory linking two infinite points having the same asymptotic eigenmodes (not modes in PT- and anti-PT-symmetric systems), demonstrating that this platform enables high-efficiency chiral transmission, with each eigenmode localized in a single waveguide. This concept is experimentally implemented in a coupled silicon waveguide system at telecommunication wavelengths. Our work provides a new evolution strategy for chiral dynamics with superior performance, laying the foundation for the development of practical chiral-transmission devices.

DOI: 10.1038/s41377-024-01409-1

Source: https://www.nature.com/articles/s41377-024-01409-1