Acoustic metamaterial lens for two-dimensional vortex beamforming and perception

Abstract

Recent advancements have identified orbital angular momentum (OAM) as a promising multiplexing strategy leveraging vortex beams to significantly enhance communication channel capacity. However, existing OAM signal demultiplexing methods, including active scanning and passive resonant techniques, encounter limitations such as reduced data transmission rates and the reliance on bulky, inefficient systems. In this work, we utilize gradient metamaterial Luneburg lens as a transformation medium to convert two-dimensional (2D) vortex beams into transmitted beams oriented in multiple directions. This approach not only improves system efficiency but also simplifies the OAM multiplexing framework. Through analysis, simulation and experiments, we verify the fast and broadband working properties of Luneburg lens constructed by non-resonant metamaterial unit cell. Additionally, by applying the coordinate transformation method, we further expand the beam separation angles achievable with the metamaterial lens. Notably, the vortex-based beamforming strategy also proves effective for multi-beam Luneburg lenses. Our work introduces a streamlined and efficient strategy for vortex detection and beam scanning, paving the way for advancements in high-speed, high-capacity acoustic communication systems and on-chip signal detection technologies.