Pure solid acoustic metasurface with coating adapter

Abstract

We propose a conceptual coating adapter design for pure solid acoustic metasurfaces with thickness to the deep subwavelength scale, wherein the coating adapter is defined as an ultra-thin soft-solid layer that can adapt to relative movements or superpose the phases of stiff plates on either side. Remarkably, by employing a special coating adapter between two stiff plates to constitute a sandwich plate, the following were successively realized: broadband double negative bands with simultaneously negative effective mass density and bulk modulus, continuous phase shifts for reflected wavefronts almost covering 0-2π range, and a pure solid two-dimensional ultra-thin broadband acoustical dark skin.