Generation of spatiotemporal acoustic vortices with arbitrarily oriented orbital angular momentum

TL;DR

This paper demonstrates the generation of three-dimensional spatiotemporal acoustic vortices with arbitrarily oriented orbital angular momentum using a 2D phased array, enabling advanced control over acoustic wave properties.

Contribution

It introduces two novel methods for controlling the orientation of acoustic OAM in 3D space, expanding the capabilities of acoustic vortex manipulation.

Findings

Successful generation of 3D ST acoustic vortices with arbitrary OAM orientation

Two approaches for OAM orientation control: vortex rotation and intersection

Potential applications in acoustic communication and particle manipulation

Abstract

Despite extensive exploration of acoustic vortices carrying orbital angular momentum (OAM), the generation of acoustic vortices with OAM orientations beyond the conventional longitudinal direction remains largely unexplored. Spatiotemporal (ST) vortices, featuring spiral phase twisting in the ST domain and carrying transverse OAM, have recently attracted considerable interest in optics and acoustics. Here, we report the generation of three-dimensional (3D) ST acoustic vortices with arbitrarily oriented OAM, thereby opening up a new dimension in acoustic OAM control. By utilizing a two-dimensional (2D) acoustic phased array, we introduce two approaches to manipulate the orientation of OAM: through the direct rotation of vortices in 3D space and the intersection of vortices carrying distinct types of OAM. These methods enable unprecedented control over the orientation of acoustic OAM, providing a new degree of freedom in the manipulation of acoustic waves. The arbitrarily oriented OAM holds promise for enhancing acoustic communication by broadening capacity and enabling more complex particle manipulation techniques. Our work establishes a foundation for future explorations into the complex dynamics of novel structured acoustic fields in the ST domain.