  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.
