Reflected wave manipulation via acoustic metamaterials with decoupled amplitude and phase

We present the analytical derivation and numerical simulation for the wavefront manipulation of reflected waves at a lossy surface. It is found that the incident plane wave can be reflected in the desired direction or conversed to the trapped surface mode without parasitic scatterings by introducing acoustic energy loss at the surface. To realize the lossy inhomogeneous surface, holey-structured acoustic metamaterial arrays with decoupled reflection amplitude and phase are used. Anomalous reflection phenomena, including non-specular reflection, negative reflection, and conversion of the propagating wave into the surface wave, are achieved by modulating the decoupled amplitude and phase. Our results provide a practical and straightforward way to manipulate the reflected waves, which can also be extended to the three-dimensional wave propagation.