Hybrid Metasurfaces for Perfect Transmission and Customized Manipulation of Sound Across Water–Air Interface

• Published in: Advanced science 2023-07, Vol.10 (19), p.e2207181-n/a
• Main Authors: Zhou, Hong‐Tao, Zhang, Shao‐Cong, Zhu, Tong, Tian, Yu‐Ze, Wang, Yan‐Feng, Wang, Yue‐Sheng
• Format: Article
• Language: English
• Subjects: acoustic metasurfaces; Acoustics; Aluminum; cross‐media manipulation; Efficiency; Hydrophobic surfaces; impedance matching; Propagation; Signal to noise ratio; Sound waves; topology optimization; water–air interface; Wireless communications
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202207181

Extreme impedance mismatch causes sound insulation at water–air interfaces, limiting numerous cross‐media applications such as ocean‐air wireless acoustic communication. Although quarter‐wave impedance transformers can improve transmission, they are not readily available for acoustics and are restricted by the fixed phase shift at full transmission. Here, this limitation is broken through impedance‐matched hybrid metasurfaces assisted by topology optimization. Sound transmission enhancement and phase modulation across the water–air interface are achieved independently. Compared to the bare water–air interface, it is experimentally observed that the average transmitted amplitude through an impedance‐matched metasurface at the peak frequency is enhanced by ≈25.9 dB, close to the limit of the perfect transmission 30 dB. And nearly 42 dB amplitude enhancement is measured by the hybrid metasurfaces with axial focusing function. Various customized vortex beams are experimentally realized to promote applications in ocean‐air communication. The physical mechanisms of sound transmission enhancement for broadband and wide‐angle incidences are revealed. The proposed concept has potential applications in efficient transmission and free communication across dissimilar media. Hybrid metasurfaces are proposed to realize perfect transmission and customized manipulation of sound across the water–air interface. Exploiting the fluid–solid interactions, an inverse‐design strategy based on topology optimization is developed to design the impedance‐matched hybrid metasurfaces. Various wavefront manipulations are demonstrated in simulations and experiments. The presented approach will facilitate potential applications of metasurfaces in cross‐media acoustic communication.