Efficient asymmetric acoustic transmission based on the combination of a binary metasurface and a gradient index metasurface

Abstract

Abstract We design and demonstrate the asymmetric acoustic transmission based on the combination of a binary metasurface (BM) and a gradient index metasurface (GIM). It yields efficient asymmetric acoustic transmission for two opposite incident directions: nearly total transmission for positive incidence but nearly total reflection for negative incidence. The underlying mechanism is ascribed to the diffraction characteristics of the BM and the GIM. We exemplify the BM and the GIM by coating unit cells consisting of three-layers of acoustic labyrinthine metamaterials, which provide full phase control and total transmission. Numerical simulations agree well with the theoretical analysis.