Observation of unidirectional negative refraction in an acoustic metafluid prism

We theoretically and experimentally demonstrate the unidirectional negative refraction in an acoustic metafluid prism. The acoustic metafluid is designed to be uniaxial and highly anisotropic in inertia. Since the directions of phase and group velocities do not coincide in the anisotropic medium, it is possible to realize the unidirectional negative refraction by the broken symmetry of phase velocity vectors with respect to the acoustic axis. Being a distinct case of the asymmetric sound propagation, the unidirectional negative refracting effect could be potentially significant in various areas such as underwater sensing, and medical ultrasonics.