Acoustic reflected wavefront modulation based on Helmholtz resonator array

In this work, a Helmholtz resonator (HR) with a subwavelength scale is proposed to modulate the acoustic wavefront in multiple manners. The phase response of the reflection wave can be continuously adjusted by altering the height of the cavity. Several HR arrays with gradient phase shifts are constructed to achieve various beam shaping phenomena, including beam deflection and beam focusing. Both the reflection angle and the focal length can be controlled by changing the phase gradients along the structure. Meanwhile, the binary design with only two kinds of HR is utilized to achieve multifunctional acoustic wavefront modulations, which extremely simplify the design philosophy. Moreover, by taking advantage of the resonance mechanism of the HR, an integrated structure composed of two HRs with different cavity volumes is adopted to achieve bifunctional acoustic wavefront modulations, making it convenient to customize the switchable device on demand. Our work offers a solution for multifunctional reflected acoustic wavefront modulations, which may have potential applications in acoustic communication, detection, and holography.