Perfect confinement of acoustic vortex by phase-gradient metacage

Acoustic wave isolation and noise reduction represent significant challenges in the field of physics and its various applications. Traditional noise control devices are often hampered by substantial size limitations and their operational efficacy is generally restricted to planar waveforms. In this work, we demonstrate the perfect confinement of acoustic vortex waves using an acoustic metacage consisting of phase-gradient metasurfaces. By leveraging the parity-reversed diffraction rule of the phase-gradient metasurfaces, the designed metacage exhibits remarkable capabilities for perfect confinement of acoustic vortex waves, showcasing robust performance even with source offsets. These findings present a promising strategy for the development of precise and adaptable acoustic confinement technologies.