Efficient scattering-free wavefront transformation with power flow conformal bianisotropic acoustic metasurfaces

Abstract

Bianisotropic metasurfaces have enabled highly efficient wavefront transformation. However, a passive and lossless bianisotropic metasurface must conserve local power at every point over the metasurface, hindering its application in handling complicated wavefields other than plane waves. In this paper, the power flow-conformal design methodology and bianisotropic unit cells are combined to comply with such a restriction. Our proposed approach provides a general recipe for arbitrary wavefront transformation with maximum power efficiency. As a demonstration, a transmission-type acoustic metasurface was designed to focus 3000 Hz plane wave airborne sound in the near field with theoretically unitary power efficiency. The metasurface was validated by both numerical simulation and experiment.