Dynamic Acoustic Beamshaping with Coupling-Immune Moir Metasurfaces

Moire effects arising from mutually twisted metasurfaces have showcased remarkable wave manipulation capabilities, unveiling tantalizing emerging phenomena such as acoustic moire flat bands and topological phase transitions. However, the pursuit of strong near-field coupling in layers has necessitated acoustic moire metasurfaces to be tightly stacked at narrow distances in the subwavelength range. Here, moire effects beyond near-field interlayer coupling in acoustics are reported and the concept of coupling-immune moire metasurfaces is proposed. Remote acoustic moire effects decoupled from the interlayer distance are theoretically, numerically, and experimentally demonstrated. Tunable out-of-plane acoustic beam scanning is successfully achieved by dynamically controlling twist angles. The engineered coupling-immune properties are further extended to multilayered acoustic moire metasurfaces and manipulation of acoustic vortices. Good robustness against external disturbances is also observed for the fabricated coupling-immune acoustic moire metasurfaces. The presented work unlocks the potential of twisted moire devices for out-of-plane acoustic beam shaping, enabling practical applications in remote dynamic detection, and multiplexed underwater acoustic communication. Coupling-immune acoustic moire metasurfaces are proposed by leveraging the interlayer coupling from propagating waves. Remote acoustic moire effects are theoretically and experimentally validated to be decoupled from the interlayer distance. The dynamic shaping of acoustic beams and vortices is successfully achieved, facilitating twisted moire devices of practical applications in remote dynamic detection and multiplexed underwater acoustic communication. image