High-fidelity cross-media acoustic holography through a passive meta-projector with synergistic amplitude-phase...

Acoustic holography has emerged as a disruptive technique for freewheelingly reconstructing the spatial sound field. However, existing mechanisms operate exclusively in homogeneous media, leaving their applications in complex cross-media scenarios beyond reach. Here, a passive meta-projector built by acoustic metamaterials is proposed and experimentally demonstrated for high-fidelity cross-media sound holography. The judiciously designed meta-projector consists of both impedance-matching and mismatching components with a subwavelength thickness and high spatial resolution. Using the full-mode expansion method, we analytically derive the acoustic transfer function of the meta-projector and reveal the existence of the quasi-decoupled point within the considered parameter space. At this point, the passive meta-projector is capable of breaking the intrinsic amplitude-phase locking relationship in conventional anti-reflection materials, thereby achieving synergistic amplitude-phase control of cross-media acoustic waves in a decoupled and ergodic way, which is crucial for high-precision holographic reconstruction. As a proof of concept, a distinct example is demonstrated both numerically and experimentally, wherein an incident underwater simple wave is precisely projected into the desired airborne complex pattern. Moreover, the potential of this meta-projector for contactless cross-media particle assembly is also illustrated. Our proposed meta-projector with multi-dimensional control establishes a new paradigm for extending the acoustic hologram to complicated cross-media systems, holding pivotal significance for diverse applications in complex media that require sophisticated manipulation, including transcranial ultrasound therapy, water-air joint communication, and so on.