Measuring the topological charges of acoustic vortices by apertures

The acoustic vortex wave has exhibited high-potential applications such as communication. In this work, the authors propose an efficient method for quantitatively measuring the topological charge of an acoustic vortex through two kinds of annular apertures: an annular triangle aperture and an annular ellipse aperture. It is found that the characteristics of the diffraction pattern in the far-field are well related with the shape of apertures and the topological charges of the acoustic vortex wave. Therefore, the topological charge of acoustic vortex beams can be determined from the diffraction patterns, which provide an effective method for measuring the topological charge of acoustic vortex beams.