Analysis of dynamic high-frequency acoustic field control by metasurfaces lens

Acoustic metasurfaces have largely been explored for acoustic field modulation, but because of their structural complexity, they are mainly implemented for airborne low frequency sound and generally located in the transmission medium, acting as a "passive acoustic field modulator." In this work, we present numerically the acoustic field modulation in water with a metasurface lens which consists of typical space-coiling structure units at high frequency (>= 1 MHz). Four kinds of materials with different physical properties were utilized as lens materials, and the lens was set at the front surface of the ultrasonic transducers, acting as an "active acoustic field modulator." The proposed investigation could be extended to allow the metasurface lens for numerous waterborne high frequency ultrasound applications. (C) 2019 Author(s).