基于梯度结构波导实现的定向声学自旋角动量密度操控  

Manipulation of directional acoustic spin angular momentum density based on gradient-structured waveguides

作　　者：张孝悦 徐华锋 陈婉娜 周农 孙文军 吴宏伟 Zhang Xiao-Yue;Xu Hua-Feng;Chen Wan-Na;Zhou Nong;Sun Wen-Jun;Wu Hong-Wei(School of Mechanics and Photoelectric Physics,Anhui University of Science and Technology,Huainan 232001,China;Center for Fundamental Physics,Anhui University of Science and Technology,Huainan 232001,China)

机构地区：[1]安徽理工大学力学与光电物理学院,淮南232001 [2]安徽理工大学基础物理研究中心,淮南232001

出　　处：《物理学报》2024年第14期127-135,共9页Acta Physica Sinica

基　　金：安徽省高校自然科学研究项目(批准号:2023AH051206,2022AH040114);安徽省高校协同创新项目(批准号:GXXT-2022-015)资助的课题.

摘　　要：近年来,人们在结构声场和声学结构表面波中发现了声波横向自旋的现象,其不仅丰富了人们对声波基本性质的理解,也为操控声波提供了新的途径.在本文中,我们设计了平整型、上凸型、下凹型的梯度声学波导,实现对声学表面波的横向自旋分布进行操控.通过理论分析和数值仿真,研究了自旋声源在3种梯度结构中激发的压力场分布以及自旋角动量密度分布,验证了近场声自旋-动量的方向锁定,展示了梯度波导中声表面波的自旋强度分布操控.研究结果可能促进对声学近场物理的对称性理解,以及提供一种操控声学自旋角动量密度的方法,为利用声波操控粒子开辟新的路径.In recent years,the discovery of the transverse spin of acoustic wave in a structural acoustic field and acoustic structural surface wave has expanded our knowledge of the basic characteristics of acoustic waves and opened up new avenues for their manipulation.On the structured surface,however,the distribution of acoustic surface waves often presents a uniform distribution,which restricts the local modification of acoustic spin angular momentum and particle manipulation capabilities.In this study,we develop some acoustic waveguides with gradients that are flat,up-convex,and down-concave in order to manipulate the lateral spin distributions of acoustic surface waves.We verify the direction-locking near-field acoustic spin-momentum,explore the pressure field distribution and the spin angular momentum density distribution of a spin acoustic source excited in each of the three gradient structures,and we also show how to manipulate the spin intensity distributions of acoustic surface waves in the gradient waveguides through theoretical analysis and numerical simulation.The numerical calculation results show that when the acoustic surface wave is excited by a clockwise rotating spin source and propagates along the left side of the waveguide,the spin angular momentum density is positive on the upper surface of the structured waveguide and negative on the lower surface.The spin angular momentum distribution and the direction of propagation of acoustic wave are entirely changed when the spin source is rotated counterclockwise.Specifically,an unequal distribution of acoustic spin angular momentum is produced by the upper convex-type waveguide and bottom concave-type waveguide when we convert the flat-type acoustic structure waveguide into a gradient-type waveguide.According to the computation results,the downconcave type waveguide exhibits a stronger density of acoustic spin angular momentum at the end and the acoustic surface waves gather at the end of the constructed waveguide.On the other hand,the waveguide collects aco

关 键 词：声学超构材料 声自旋角动量 定向声传输 梯度声学波导 

分 类 号：O42[理学—声学]