Dynamic manipulation of ultrasonic beams by coding Moiré metasurfaces

Abstract

Dynamic acoustic beam manipulation via tunable acoustic metasurfaces (AMs) has attracted significant attention. However, most current tunable AMs are primarily designed for airborne sound, feature complex structural components, and serve a singular purpose. This study proposes a coding Moiré metasurface (CMM) consisting of two cascaded acoustic coding metasurfaces (ACMs) to dynamically manipulate ultrasonic beams in water. The CMM merges the characteristics of Moiré AMs and coding and can achieve different ultrasonic beam manipulations by rotating the ACM and changing the coding sequence. This is demonstrated by presenting CMMs with stripe and checkerboard coding patterns: the former split an ultrasonic beam into two dynamically omnidirectional scanning beams, while the latter divided it into four sections. Finally, two coding bits are employed to construct the CMM samples: a water unit for bit “0” and a photosensitive resin unit for bit “1.” Experimental results demonstrate that the CMM can dynamically manipulate ultrasonic beams. The proposed CMMs hold substantial potential for acoustic communication and dynamic detection applications.