High-order Acoustic Bessel Beam Generation by Spiral Gratings

We report first-order Bessel beam formation by means of a novel passive acoustic device. The scattering of plane waves by a spiral grating leads to the creation of an acoustic vortex with a pressure null on-axis. Numerical simulations and experimental results report the formation of an acoustic vortex in the near field as the phase presents a screw dislocation and the field is null at the axis. The control of the vorticity and the characteristics of Bessel beams are useful for potential applications on low-cost acoustic tweezers and acoustic radiation force applications.