Far-field acoustic modulation based on arbitrarily curved 1-bit coding metasurfaces

Recently, the notion of coding has been introduced to the design of metasurfaces, which needs only several units to construct metasurface and provides an intelligent platform to modulate waves. However, most of the existing coding metasurfaces are flat, which cannot fulfill the special demands for curved shapes in practice. This paper provides an arbitrarily curved 1-bit coding metasurface to steer the far-field acoustic waves. The far-field radi-ation form by the curved coding metasurface is derived theoretically. To achieve the desired diffraction patterns, an optimization method based on genetic algorithm is developed for customized inverse design of the coding sequence. Full wave simulations for curved metasurfaces with circular, parabolic, and sinusoidal shapes are implemented by the finite element method. Influences of curvature radius are discussed. Experimental verifi-cations for directional refraction, symmetric and asymmetric beam splitting are also performed for circular coding metasurfaces. The results show that the sidelobes in undesired directions can be effectively suppressed through the optimization of the coding sequence, which makes it is easy to realize asymmetric beam splitting. The present study provides an important theoretical guidance for design of an arbitrarily curved coding meta-surface and manipulation of acoustic waves.