Unidirectional acoustic transmission through a prism with near-zero refractive index

We propose a two-dimensional model of acoustic prism comprising metamaterials with near-zero refractive index to yield high efficiency unidirectional transmission and demonstrate an implementation by coiling up space. Due to the acoustic tunneling effect, the waveform is kept consistent between input and output waves, and the transmitted angle can be controlled by reshaping the prism, even in the presence of hard scatterer. A directional waveguide is also designed whose transmission property can be freely switched between all possible states. Our design may have potential for practical applications of acoustic one-way devices in various fields such as ultrasound imaging and treatment. (C) 2013 AIP Publishing LLC.