Amplitude-phase metasurface for the manipulation of diffraction-free spoof surface acoustic waves

The integration of Airy beams with spoof surface acoustic waves (SSAWs) establishes Airy beams as an interfacial “information carrier” or “acoustic tweezer,” offering exceptional potential for advanced surface wave control. However, current SSAW-based Airy beams are excited purely through phase modulation (PM), and the lack of amplitude adjustability severely compromises their flexibility in precise wavefront control. Here, we design an amplitude-phase modulated acoustic metasurface composed of multi-cavity structure and slotted baffle, which, in combination, constitute “0” and “1” structural units. We realize independent control over transmittance from 0 to 1 of SSAWs under 0/π binary phases by separately tuning the cavity depth and slot width. Programable control of amplitude-phase distribution has been demonstrated by several examples. First, we validate the feasibility of generating high-quality Airy beams and Airy-Talbot beams, observing the self-imaging of nonperiodic signals along the curved trajectory. In addition, by symmetrically focusing two Airy beams, we realize acoustic focusing with a large focal depth, exhibiting outstanding self-healing performance. Our design overcomes the limitations of pure PM in exciting Airy beams, which is expected to provide a compact integrated platform for on-chip acoustic communication or microfluidics.