Manipulation of transmitted wave front using ultrathin planar acoustic metasurfaces

Abstract

Nowadays, the acoustic devices are developing toward miniaturization. However, conventional materials can hardly satisfy the requirements because of their large size and complex manufacturing process. The introduction of acoustic metasurfaces has broken these restrictions, as they are able to manipulate sound waves at will by utilizing ultrathin planar metamaterials. Here, a simple acoustic metasurface is designed and characterized, whose microstructure is constructed with a cavity filled with air and two elastic membranes on the ends of cavity. By appropriately optimizing the configurations of microstructures, the steering of transmitted wave trajectory is demonstrated, and some extraordinary phenomena are realized at 3.5 kHz, such as planar acoustic axicon, acoustic lens, the conversion from spherical waves to plane waves, and the transformation from propagating waves to surface waves.

Apparent Negative Reflection with the Gradient Acoustic Metasurface by Integrating Supercell Periodicity into the Generalized Law of Reflection

“…Similar to their electromagnetic counterparts, acoustic metasurfaces have become attractive for they are able to engineer the phase profiles of the impinging waves by the artificial designed structures with subwavelength thickness instead of the space consuming solutions offered by the traditional diffractive acoustic devices. Numerous types of acoustic meta-atoms have been proposed to construct the functional acoustic metasurfaces, such as tapered labyrinthine structure14, coiling-up slit structure1516, zigzag channel17, Helmholtz resonator array18, split sphere19 and membrane based structure20. Based on these acoustic meta-atoms, a great number of acoustic wavefront manipulation devices have been constructed and operated successfully, for example, the acoustic focusing lens2122, acoustic vortex beam generator23, acoustic Airy beam generator2425, acoustic carpet cloaking2627 and so on.…”

Acoustic Metamaterials in Aeronautics

“…Coiled-up space devices and resonant membranes were intrinsically designed to lead to metasurfaces, and hence, the majority of the so-based work presented in previous paragraphs classifies as metasurfaces, due to their deep sub-wavelength thickness. However, for each of the approaches presented above, some engineered metasurfaces can be found in the literature [31][32][33][34][35]. A very interesting superabsorber with micro-bubble insertions was presented in [36].…”

Acoustic carpet cloak based on an ultrathin metasurface

“…Recently, Helmholtz resonators [28][29][30] and membrane [32] and pentamode metamaterial [33] based unit cells have been proposed as acoustic metasurface unit-cell designs to control the phase of the acoustic wave. However, most of these studies on metasurface unit-cell designs still suffer from being bulky, having limited bandwidth, high losses, and nonuniform reflected/transmitted wave amplitude and do not present the aptitude for reconfigurability.…”