Holographic tomography of dynamic three-dimensional acoustic vortex beam in liquid

Abstract

Acoustic vortex beams have attracted significant research interest in the last decade. The orbital angular momentum provides an additional degree-of-freedom, hence attracting attention in physics and technology. Generation and measurement are important parts of acoustic vortex research. For the production of acoustic vortices, it is convenient and less costly to use passive materials. Moreover, a point-by-point scanning procedure with a hydrophone still remains the commonly used method and is cumbersome to measure a three-dimensional acoustic field. However, an acoustic vortex field is usually three-dimensional, dynamic, and complex. Thus, the demand for imaging methods for complex pressure distributions has emerged. Herein, we introduced an improved hybrid single-arm coiling slit to generate an acoustic vortex with a deep potential well and infirm focusing. In addition, we proposed a method for holographic reconstruction and visualization of a three-dimensional acoustic field, which does not destroy the acoustic field information. The spatial-temporal properties of the acoustic vortex in the experiment closely match that of theoretical prediction. This study provides a reference for the manipulation and representation of a three-dimensional underwater acoustic wave.