Characterization of phased array-steered acoustic vortex beams

Acoustic vortex (AV) beams generation is a subject of current interest. Even though different applications have been proposed using AV, their potential of use is still to be explored. Recent research works on particle manipulation use phased array systems for AV generation because it allows a flexible beam configuration, i.e., the beam can be easily focalized and modified in its shape. However, little attention has been paid to the fact that the AV can also be electronically steered. In view of this, this work presents a study of the steering capability of an AV. In particular, this paper gives an analysis of the effect of the applied delay law on the structure of AV beams steered at different angles using an array transducer of 32 equidistant elements, deployed on a triangular lattice, operating at 40 kHz. Special attention is paid to the appearance of grating vortices. The effect of the individual element directivity on the resultant beam is also studied. Experimental measurements were carried out in order to validate numerical estimations. Obtained results paves the way for the use of electronically steered vortices in different applications. Also, the potential of use of acoustic grating vortices is discussed.