Metasurface-driven angle-insensitive acoustic communication with high information capacity

키워드

확장요약문

Acoustic communication is inherently constrained by limited usable frequency bandwidth, and compact autonomous robotic platforms require miniaturized, low-power receiver. Orbital angular momentum (OAM) has emerged as a promising degree of freedom for enhancing communication capacity across radio-frequency, optical, and acoustic communication systems, by enabling the multiplexing of mutually orthogonal channels at the same carrier frequency. However, conventional OAM receiving systems rely on bulky phased arrays, or suffer from degraded OAM mode discrimination performance when the incoming beam is tilted. To address these limitations, we propose an acoustic metasurface receiver capable of sorting OAM modes regardless of the angle of incidence. Its phase profile untwists each OAM mode with a conjugate helical phase and focuses it onto its own port with a quadratic phase, so that a tilted incidence only shifts all focal spots together. This enables independent identification of varying incident angles and different OAM modes. Numerical simulations demonstrate that the proposed metasurface can discriminate distinct OAM modes over a wide range of incidence angles up to 50°, focusing each mode onto receiving transducers placed at separate locations. This design principle is expected to be applicable not only to acoustic communication but also to optical interfaces that convert free-space-propagated high-dimensional OAM-based qudits into chip-integrated path-encoded qudits.