Fig. 1.

Metasurface-based acoustic lens. a Convergence of acoustic energy by the metasurface lens after a normally incident plane wave transmits through it. Through proper design of the individual unit elements and their arrangement, different focusing schemes can be achieved, as presented in the insets. b Schematic representation of the acoustic metasurface lens. It consists of N slits that are periodically perforated in a thin plate with a spacing of s and a depth of h. The width and phase shift of the mth slit are denoted by w_m and ϕ_m, respectively