Helmholtz‐Resonator Metasurface Based High‐Efficiency Acoustic Focusing Lens.

The high‐efficiency transmitted acoustic focusing lenses based on the Helmholtz resonator (HR) metasurface is reported. The proposed lenses demonstrate superior focusing performances, which can provide deep‐subwavelength resolution. The proposed lenses demonstrate superior focusing performances, in which the performances of acoustic focusing metasurface is investigated in details and the bandwidth of the metasurface with hybrid resonant structures is broadened. For the former, the effects of different numerical apertures, different focusing distances, and different incidence angles are investigated. At the same time, off‐axis focusing and spherical wave focusing lenses are also demonstrated. For the latter, by spacing the HR elements with different resonant frequencies, a broad‐band acoustic lens is also designed and achieved, in which the favorable focusing performance can be realized in a relative wider frequency range. The proposed designs provide great potential applications in many scenarios, such as nondestructive testing, ultrasonic medical treatment and so on. [ABSTRACT FROM AUTHOR]