Flexible wavefront manipulations via amplitude-phase joint coding acoustic metasurfaces

Abstract

Acoustic coding metasurfaces (ACMs) with limited kinds of meta-atoms have attracted much attention due to flexible wavefront manipulations of acoustic waves. However, the previously reported ACMs are mainly encoded by phase responses, limiting their functions and applications. For complete manipulation of the propagation of acoustic waves, it is beneficial to control both amplitude and phase responses. In this paper, amplitude-phase joint coding acoustic metasurfaces (APCMs) are proposed, which enable simultaneous realization of acoustic wavefront engineering and energy allocation. In particular, by adjusting the geometrical parameters of the proposed dual-layer meta-atoms, the reflection amplitude can be continuously controlled from approximate total absorption to total reflection, and the full reflection phase coverage can be realized. Two examples are proposed to verify the abilities of APCMs. The direction and intensity of the reflected beam can be manipulated. Meanwhile, the position and intensity of focal spots can be arbitrarily modulated by different amplitude-phase sequences of coding elements. The full-wave numerical simulation results confirm the effectiveness of the proposed APCMs, which have potential applications in noise control and advanced field-manipulation systems.