Space-time-frequency multiplexed orbital angular momentum generation via acoustic rotating point sources: Methodology and coherence characterization
Phys. Rev. Applied 26, 014054 – Published 20 July, 2026
DOI: https://doi.org/10.1103/9pmr-mz15
Abstract
Optical and acoustic communications based on orbital angular momentum (OAM) offer an additional degree of freedom for enhancing information capacity, yet practical implementations of broadband space-time-frequency division multiplexing (STFDM) remain challenging due to system complexity and limited tunability, particularly at low frequencies. Here, we demonstrate a compact and efficient method for broadband STFDM using acoustic rotating point sources (ARPS). We show that a single ARPS can generate multiple high-purity OAM modes with tunable topological charges, whose frequencies are intrinsically linked to the rotational Doppler effect. This mechanism enables simultaneous space, time, and frequency multiplexing within a single transmission path, while significantly reducing the number of required transmitters compared with conventional active array-based approaches. Of note, the proposed method operates continuously from low to high frequencies, extending broadband STFDM to low-frequency acoustic regimes that are particularly relevant for underwater communication. Moreover, we experimentally reveal, for the first time, the coherence properties of multiple acoustic OAM modes with identical topological charges and exploit this property to enhance the stability of high-order modes and mitigate mode crosstalk in OAM-based communication. This work provides a compact and versatile approach for OAM-based acoustic communication, paving the way for future high-capacity multiplexing systems.
