Acoustic surface modes on metasurfaces with embedded next-nearest-neighbor coupling

Abstract

We design, simulate, and experimentally characterize an acoustic metasurface comprising of a one-dimensional (1D) array of open, sound-hard cavities modulated with beyond-nearest-neighbor (BNN) couplings in the form of additional connecting cavities embedded beneath the surface. The hidden complex structure is realized readily with additive manufacturing techniques [three-dimensional (3D) printing]. The dispersive properties of the supported localized acoustic surface waves are influenced by competing power-flow channels provided by the BNN couplings, that generate extrema in the dispersion spectra within the first Brillouin zone. The structure supports negatively dispersing ``backwards'' waves that we experimentally verify. Such structures thereby provide a route to enhanced acoustic sensing by acoustic metasurfaces.