摘要
螺旋二色性利用无限的轨道角动量自由度,可以突破依赖于固有自旋自由度的圆二色性所受到的两态限制,为探索经典波体系中的手性效应提供了重要的手段.然而,在波与物质相互作用过程中,手性信号通常非常微弱,使得螺旋手性效应的有效增强极具挑战性.本文通过在非厄米梯度超构表面的内禀拓扑荷中构建手性奇异点,提出了一种实现最大螺旋二色性的新范式.由于奇异点所诱发的非对称手性耦合特性,非厄米梯度超构表面可以通过灵活地设计,实现多样化的极端手性调控:一种手性的涡旋场被非厄米超构表面完全反射,而相反手性的涡旋场则可以被完美吸收或传输到定制的涡旋模式.作为最大螺旋二色性的一种体现,本文提出完美手性选择的涡旋传输现象,并通过声学实验进行了验证.本研究为实现最大手性效应以及探索波与物质相互作用中的手性物理提供了新途径,有望推动诸如非对称手性调控、单向传播和信息多路复用等轨道角动量相关的基础研究和应用领域的发展.
Helical dichroism(HD)utilizing unbounded orbital angular momentum degree of freedom,has provided an important means of exploring chiral effects in diverse wave systems,surpassing the two-state constraint in circular dichroism that relies on intrinsic spin.However,the naturally feeble chiral signals that arise during wave-matter interactions pose significant challenges to the effective enlargement of HD.Here,we introduce a new paradigm for realizing maximum HD through non-Hermitian gradient metasurfaces by engineering a chiral exceptional point(EP)in intrinsic topological charge.The nonHermitian gradient metasurfaces are empowered by the asymmetric coupling feature at the EP,enabling flexible construction to realize versatile chirality control in extreme circumstances where one chiral vortex is totally reflected and the opposite counterpart is completely absorbed or transmitted into the customized vortex modes.As the manifestation of the maximum HD,we present the first experimental demonstration of perfect chirality-selected vortex transmission in acoustics.Our findings open new venues to achieve maximum chirality and explore chiral physics of wave-matter interactions,which can boost many vortical applications in asymmetric chirality manipulation,one-way propagation,and information multiplexing.
作者
李潇
胡传捷
田源
刘友文
陈焕阳
徐亚东
卢明辉
伏洋洋
Xiao Li;Chuanjie Hu;Yuan Tian;Youwen Liu;Huanyang Chen;Yadong Xu;Ming-Hui Lu;Yangyang Fu(College of Physics,Nanjing University of Aeronautics and Astronautics,Nanjing 211106,China;Key Laboratory of Aerospace Information Materials and Physics,Ministry of Industry and Information Technology,Nanjing 211106,China;Department of Physics,Xiamen University,Xiamen 361005,China;dNational Laboratory of Solid State Microstructures and Department of Materials Science and Engineering,Nanjing University,Nanjing 210093,China;School of Physical Science and Technology&Jiangsu Key Laboratory of Thin Films,Soochow University,Suzhou 215006,China;State Key Laboratory of Mechanics and Control for Aerospace Structures,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China)
基金
supported by the National Natural Science Foundation of China(12274225,11974010,12274313,92050102,and12374410)
the Natural Science Foundation of Jiangsu Province(BK20230089)
the National Key R&D Program of China(2022YFA1404300 and 2022YFA1404400)
the Fundamental Research Funds for the Central Universities(NE2022007,20720220033,and 20720230102)。
