Broadband Airy-like beams by coded acoustic metasurfaces

We propose a coded acoustic metasurface (CAM) to generate Airy-like beams (ALBs) in air. A space-folding structure is designed to act as the bit “1” unit of the CAM, and an air unit with the same size is used as the bit “0”. Finite-element simulations demonstrate that the ALBs generated by this simple CAM have excellent self-accelerating, self-healing, and non-diffracting features. It is found that the bit “1” unit works well in a large frequency range of 6–9 kHz, and the CAM, therefore, generates a broadband ALB. Furthermore, two symmetrical CAMs are employed to compose a lens for realizing the acoustic focusing in the frequency range of 6–9 kHz, and the focal length of the CAM lens is sensitive to the working frequency. The work presented here could greatly benefit acoustic imaging, particle trapping and manipulation, and broadband acoustical devices.