Continuously Tunable Acoustic Metasurface with Rotatable Anisotropic Three-component Resonators

We propose a tunable acoustic metasurface consisting of identical units. And units are rotatable anisotropic three-component resonators, which can induce the non-degenerate dipolar resonance, causing an evident phase change in low frequencies. Compared with the monopole resonance widely used in Helmholtz resonators, the polarization direction of the dipole resonance is a new degree of freedom for phase manipulation. The proposed metasurface is constructed by identical units that made with real (not rigid) materials. And the phase profile can continuously change by rotating the anisotropic resonators. We present a wide-angle and broad-band acoustic focusing by the metasurface under a water background.