Superresolution using an acoustic vortex wave antenna

Abstract

In this paper, we demonstrate far-field acoustic superresolution using shaped acoustic vortices. Compared with previously proposed near-field methods of acoustic superresolution, in this work we describe how far-field superresolution can be obtained using an acoustic vortex wave antenna. This is accomplished by leveraging the recent advances in optical vortices in conjunction with the topological diversity of a leaky wave antenna design. In particular, the use of an acoustic vortex wave antenna eliminates the need for a complicated phased array consisting of multiple active elements, and enables a superresolving aperture to be achieved with a single simple acoustic source and total aperture size less than a wavelength in diameter. A theoretical formulation is presented for the design of an acoustic vortex wave antenna with arbitrary planar arrangement, and explicit expressions are developed for the radiated acoustic pressure field. This geometric versatility enables variously-shaped acoustic vortex patterns to be achieved, which propagate from the near-field into the far-field through an arrangement of stable integer mode vortices. Two examples are presented and discussed in detail, illustrating the generation and transmission of an "X" and "Y" shape into the far-field. Despite the total aperture size being less than a wavelength in diameter, the proposed acoustic vortex wave antenna is shown to achieve far-field superresolution with feature sizes 4-9 times smaller than the resolution limit.

Particle Assembly with Synchronized Acoustic Tweezers

“…It is also noteworthy to underline that the calculations of the force and torque exerted by a vortex beam, initially calculated for spherical particles have been recently extended to nonspherical particles with the use of the T-matrix method [17,24,25]. * michael.baudoin@univlille.fr Experimentally, the approaches for the synthesis of acoustical vortices can be divided into three categories: The first one, that we will refer as the active array method, relies on arrays of transducers whose phase and/or amplitude can be tuned to synthesize a vortex in the surrounding fluid [1,4,7,19,20,22,[26][27][28][29][30][31]. The advantage of this method is that the vortex core (and thus the acoustical trap) can be moved electronically [4,5,28,30] and multiple traps can be synthesized simultaneously [8].…”