Redirection of sound waves using acoustic metasurface

When acoustic waves are impinged on an impedance surface in fluids, it is challenging to alter the vibration of fluid particles since the vibrational direction of reflected waves shares the same plane of the incidence and the normal direction of the surface. We demonstrate a flat acoustic metasurface that generates an extraordinary reflection, and such metasurface can steer the vibration of the reflection out of the incident plane. Remarkably, the arbitrary direction of the extraordinary reflection can be predicted by a Green's function formulation, and our approach can completely convert the incident waves into the extraordinary reflection without parasitic ordinary reflection.