Date of Award
1-1-2025
Document Type
Dissertation
Degree Name
Ph.D. in Physics
First Advisor
Likun Zhang
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Vortex beams carrying angular momentum arise from a phase gradient in the azimuthal direction, which is known as intrinsic orbital angular momentum (OAM). When such a beam propagates through layered or inhomogeneous media, the intrinsic OAM and extrinsic OAM (originating from the motion of the beam’s center) interact and transfer between each other. This interaction results in a transverse shift of the wave field out of the incident plane, a phenomenon referred to as the acoustic Hall effect.
This dissertation investigates the fundamental wave dynamics of the acoustic Hall effect for angular momentum carrying acoustic waves interacting with metasurfaces. Metasurfaces offer the ability to manipulate wavefronts in ways that natural materials cannot. Through the introduction of metasurfaces, this study explores the fundamental wave dynamics using theoretical analysis, numerical calculations, and experimental measurements.
Specifically, we report the first experimental observation of the acoustic orbital Hall effect using vortex beams generated by four speakers interacting with a metasurface in air. Our measurements reveal the asymmetry of the pressure fields and the shift of gravity center, which are linked to asymmetries in the axial energy and transverse angular momentum. A notable method is demonstrated to separate the axial angular momentum field into reconstructed symmetric vortex beams and a diffracting background. We discuss the conservation of angular momentum along the metasurface’s phase gradient direction. Furthermore, we investigate the Hall effect across different frequencies and analyze the temporal evolution of both linear and angular momentum in the vortex beams. The Huygens method and a delay-and-sum method are used to calculate the field for comparison with experimental data. Higher-order vortex beams are also studied based on simulation results. Bessel vortex beams are analyzed via the angular spectrum method, representing the non-diffracting case as a supplement to diffracting vortex beams in experiments. A refined theory of the transverse shift for obliquely incident vortex beams is briefly presented.
This research not only provides the first experimental observation of the orbital acoustic Hall effect but also offers a physical understanding and simulation comparison of the observed phenomena. It has the potential to inspire new theoretical developments of the Hall effect beyond the paraxial approximation and to impact the application of vortex beams in complex environments.
Recommended Citation
Gong, Xinyue, "Hall Effect of Angular Momentum Carrying Acoustic Waves Interacting with Metasurfaces" (2025). Electronic Theses and Dissertations. 3283.
https://egrove.olemiss.edu/etd/3283