Systematic design and experimental demonstration of bianisotropic metasurfaces for scattering-free manipulation of acoustic wavefronts

Abstract

Recent advances in gradient metasurfaces have shown that by locally controlling the bianisotropic response of the cells one can ensure full control of refraction, that is, arbitrarily redirect the waves without scattering into unwanted directions. In this work, we propose and experimentally verify the use of an acoustic cell architecture that provides enough degrees of freedom to fully control the bianisotropic response and minimizes the losses. The versatility of the approach is shown through the design of three refractive metasurfaces capable of redirecting a normally incident plane wave to 60°, 70°, and 80° on transmission. The efficiency of the bianisotropic designs is over 90%, much higher than the corresponding generalized Snell’s law based designs (81%, 58%, and 35%). The proposed strategy opens a new way of designing practical and highly efficient bianisotropic metasurfaces for different functionalities, enabling nearly ideal control over the energy flow through thin metasurfaces.

Symmetry breaking creates electro-momentum coupling in piezoelectric metamaterials

“…A series of theoretical studies were carried out to characterize Willis coupling and understand its physical origins [18][19][20][21][22][23][24][25][26]. Guided by accompanying predictions that Willis coupling is connected with unusual phenomena such as asymmetric reflections and unidirectional transmission, recent experimental realizations of Willis metamaterials that demonstrate these phenomena were reported [27][28][29][30][31][32][33][34][35]. To date, these investigations were limited to metamaterials that are deformable only by mechanical forces.…”

High-efficiency anomalous splitter by acoustic meta-grating

“…Under an oblique incidence with a large angle, the coupling effect becomes prominent, and generates unexpected inside lobes (higher orders of diffractions). To overcome this drawback, bi-anisotropic metasurfaces 21,22 , which could redirect the normal incident wave to large angles with over 90% efficiency has been suggested. However, they still suffer from the sub-wavelength unit cells and imperfect performance.…”

Improving directional radiation quality based on a gradient amplitude acoustic leaky wave antenna

“…Acoustic metasurfaces as a new kind of planer profile metamaterials have open up a new avenue for acoustic wavefront manipulation [13]. Over the past few years, we have witnessed considerable interest in acoustic metasurfaces, which could modulate refracted/reflected waves by introducing discrete phase variations from 0 to 2p along their surface [14][15][16]. In general, the generalized acoustic Snell's law is widely utilized to provide Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.…”