Department of Mechanical Engineering, Boston University, Boston, MA, 02215, USA.
Department of Radiology, Boston University Medical Campus, Boston, MA, 02118, USA.
Nat Commun. 2018 Apr 10;9(1):1349. doi: 10.1038/s41467-018-03839-z.
Acoustic metasurfaces represent a family of planar wavefront-shaping devices garnering increasing attention due to their capacity for novel acoustic wave manipulation. By precisely tailoring the geometry of these engineered surfaces, the effective refractive index may be modulated and, consequently, acoustic phase delays tuned. Despite the successful demonstration of phase engineering using metasurfaces, amplitude modulation remains overlooked. Herein, we present a class of metasurfaces featuring a horn-like space-coiling structure, enabling acoustic control with simultaneous phase and amplitude modulation. The functionality of this class of metasurfaces, featuring a gradient in channel spacing, has been investigated theoretically and numerically and an equivalent model simplifying the structural behavior is presented. A metasurface featuring this geometry has been designed and its functionality in modifying acoustic radiation patterns experimentally validated. This class of acoustic metasurface provides an efficient design methodology enabling complete acoustic wave manipulation, which may find utility in applications including biomedical imaging, acoustic communication, and non-destructive testing.
声超表面是一类平面波前整形器件，由于其具有新颖的声波操控能力而受到越来越多的关注。通过精确地设计这些工程表面的几何形状，可以调制有效折射率，从而调节声波的相位延迟。尽管已经成功地展示了使用超表面进行相位工程，但幅度调制仍然被忽视。在这里，我们提出了一类具有喇叭状空间螺旋结构的超表面，实现了同时具有相位和幅度调制的声控制。本文理论和数值研究了具有通道间距梯度的这一类超表面的功能，并提出了简化结构行为的等效模型。设计了具有这种几何形状的超表面，并通过实验验证了其在改变声辐射模式方面的功能。这种声超表面提供了一种有效的设计方法，可以实现完全的声波操控，在包括生物医学成像、声通信和无损检测在内的应用中可能具有实用价值。
