Power-flow-tracing metamirrors for underwater acoustic focusing

Acoustic metasurfaces have attracted significant interest due to their unique capabilities for wave-field manipulation, opening up novel avenues for a wide range of applications. Unlike conventional metasurfaces employing local phase-shifting units, an emerging approach based on power-flow-conformal design has emerged for sound redirection with higher efficiency. In this work, we present underwater metasurfaces designed via the power-flow-tracing methodology that enable precise tailoring of complex reflection fields. As a proof of concept, a metamirror is constructed capable of focusing underwater sound. Furthermore, experimental demonstrations are performed to validate the efficiency of the proposed metamirror designs. Our findings offer valuable insight for controlling acoustic fields in underwater environments and may inspire the development of related underwater acoustic devices and medical ultrasound equipment.