Wavefront manipulation based on transmissive acoustic metasurface with membrane-type hybrid structure

We designed and demonstrated a gradient acoustic metasurface to manipulate the transmissive wavefront. The gradient metasurface is composed of eight elements based on membrane-type hybrid structures, whose thickness and width are about 1/5 and 1/20 of the incident wavelength, respectively. Here, we employ acoustic theory to analyze the transmission spectrum and phase gradient of the metasurface, the properties of high transmission efficiency and discrete phase shifts over the full 2 π range can be achieved simultaneously. By appropriate selection of the phase profile along the transverse coordinate of the metasurface or the angle of incident wave, the transmissive wavefront manipulations based on metasurface can be obtained as expected from the generalized Snell’s law, such as anomalous refraction, acoustic cloak based on flat focusing, acoustic self-bending beam, conversion of propagating wave to surface wave and negative refraction. Our gradient metasurface may have potential application in low-loss acoustic devices.