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Lotus Metasurface for Wide-Angle Intermediate-Frequency Water–Air Acoustic Transmission

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posted on 2021-10-27, 14:36 authored by Zhandong Huang, Zhipeng Zhao, Shengdong Zhao, Xiaobing Cai, Yiyuan Zhang, Zheren Cai, Huizeng Li, Zheng Li, Meng Su, Chuanzeng Zhang, Yaozong Pan, Yanlin Song, Jun Yang
Only 0.1% of the acoustic energy can transmit across the water–air interface because of the huge acoustic impedance mismatch. Enhancing acoustic transmission across the water–air interface is of great significance for sonar communications and sensing. However, due to the interface instability and subwavelength characteristics of acoustic metamaterials, wide-angle intermediate-frequency (10 kHz-100 kHz) water–air acoustic transmission remains a great challenge. Here, we demonstrate that the lotus leaf is a natural low-cost acoustic transmission metasurface, namely, the lotus acoustic metasurface (LAM). Experiments demonstrate the LAM can enhance the acoustic transmission across the water–air interface, with an energy transmission coefficient of about 40% at 28 kHz. Furthermore, by fabricating artificial LAMs, the operating frequencies can be flexibly adjusted. Also, the LAM allows a wide-angle water-to-air acoustic transmission. It will enable various promising applications, such as detecting and imaging underwater objects from the air, communicating between ocean and atmosphere, reducing ocean noises, etc.