Acoustic planar surface retroreflector

This article reports on the design, numerical simulation, fabrication, and experimental test of an acoustic planar retroreflector capable of effectively reflecting sound along its incident direction for a wide operating angle range (0-70). The proposed acoustic planar retroreflector is a compound of two cascaded metasurfaces: a transmissive surface that converges the incident beam onto a second planar surface placed behind it, which serves as a reflective surface that bounces the beam back along the incident direction. Both the simulated and measured results provide evidence of the sound retroreflection effect. The structure proposed here provides a possible strategy for improving medical ultrasound, underwater communication, and illusion device design.