Broadband Tunable Acoustic Asymmetric Focusing Lens from Dual-Layer Metasurfaces

We report both experimentally and numerically that a broadband acoustic lens with asymmetric focusing is realized by dual-layer metasurfaces in air. The acoustic waves can be focused on a side with 0.4 wavelength resolution focusing characteristic, but cannot transmit through the lens in a large range of incident angles on the other side. This exotic phenomenon exists in the range of 2910-3610 Hz, which arises from the asymmetric phase manipulation induced from the dual-layer metasurfaces. More importantly, without changing the structure of both metasurfaces, the horizontal and vertical positions of the focus can be systematically manipulated by mechanically changing the distance between both metasurfaces and the incident angle, respectively. The proposed lens has the advantages of broadband multifunctionality, subwavelength focusing, planar structure, and tunable properties, showing promising applications in focused ultrasound therapy and medical ultrasound imaging.

Duke Scholars

Author Jianping Xia