物理学报2024，Vol.73Issue(14)：112-120,9.DOI:10.7498/aps.73.20240484
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
摘要
Abstract
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 down-concave 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 acoustic waves close to the structure center when it is an up-convex structural waveguide.The findings can open up new avenues for manipulating particles using acoustic waves,by providing a means for controlling the acoustic spin angular momentum density and improving our understanding of symmetry in acoustic near-field physics.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Key words
acoustic metamaterials/acoustic spin angular momentum/unidirectional sound propagation/gradient acoustic waveguides引用本文复制引用
张孝悦,徐华锋,陈婉娜,周农,孙文军,吴宏伟..基于梯度结构波导实现的定向声学自旋角动量密度操控[J].物理学报,2024,73(14):112-120,9.基金项目
安徽省高校自然科学研究项目(批准号:2023AH051206,2022AH040114)和安徽省高校协同创新项目(批准号:GXXT-2022-015)资助的课题. Project supported by the Natural Science Foundation of the Higher Education Institutions of Anhui Province,China(Grant Nos.2023AH051206,2022AH040114)and the University Synergy Innovation Program of Anhui Province,China(Grant No.GXXT-2022-015). （批准号:2023AH051206,2022AH040114）
