A Study On Phase Modulation Of Acoustic Vortex Beam With Metasurfaces

A transmitted acoustic metasurface refers to a flattened material or structure which's thickness is less than one wavelength,and less than one wavelength is also referred to as a subwavelength.Such materials or structures have extraordinary physical properties that natural materials do not have,such as negative refraction,arbitrary focus acoustic focusing,acoustic plane wave to acoustic vortex wave conversion,and the like.Ultra-surfaces with ultra-thin dimensions of specific performance were first proposed in the field of electromagnetism and later attracted the attention of acoustic researchers.They have been cited in the field of acoustics.In recent years,various acoustic metasurfaces with excellent performance have been introduced.It has been proposed that the application of acoustic metasurfaces is also endless,such as non-contact acoustic spanner and screwdrivers,underwater acoustic communication using acoustic vortex waves generated by acoustic metasurfaces,and manipulation of cell motion by acoustic waves generated by acoustic metasurfaces.The main advantage of the acoustic matesurface is that it has a subwavelength thickness and a good degree of impedance matching,and such an acoustic device is easy to be miniaturized and integrated.This paper first studies the design process of acoustic matesurface,and explains how the acoustic matesurface transforms acoustic plane waves into acoustic vortex waves.The influence of the phase arrangement of the acoustic supersurface unit cell on the acoustic vortex wave topological charge is also analyzed,and the acoustic vortex wave is generated by the designed acoustic matesurface in the finite element numerical analysis software.Then,four kinds of modulation methods of the phase of the acoustic vortex wave are studied: First,the phase of the acoustic vortex wave is controlled by changing the type of filling gas in the acoustic matesurface;Second,by changing the temperature of the filling gas in the acoustic matesurface to modulate the phase of the acoustic vortex wave;Third,the phase of the acoustic vortex wave is modulated by a combination of two acoustic super surfaces.Fourth,the acoustic vortex wave is converted into a sound plane wave by a combination of three acoustic metasurfaces.Finally,the principle of acoustic metasurface realization of Bessel acoustic focusing and Bessel beam generation is studied,and a new acoustic metasurface is designed to realize wide-band Bessel acoustic focusing and generate Bessel beam.