Hybrid intelligent strategy driving high-dimensional encrypted orbital angular momentum comb multicasting towards optical data-transmission networks

As global data traffic continues to grow rapidly, modern optical communication systems are approaching the capacity limits of conventional multiplexing technologies. Expanding the usable degrees of freedom of light has therefore become an important direction for next-generation high-capacity optical networks. Among various physical dimensions of light, orbital angular momentum (OAM) has attracted considerable attention because of its theoretically unbounded and mutually orthogonal modal states, which offer a natural platform for high-dimensional optical information encoding.

Existing OAM communication systems are mainly based on orbital-angular-momentum shift keying (OAM-SK) or mode-division multiplexing (OAM-DM), where each OAM mode is treated as an independent information carrier. Although these approaches have demonstrated high-capacity transmission, they typically require complicated multi-path optical architectures and bulky modulation systems, limiting scalability and real-time operation. Moreover, most current schemes rely on single-mode or low-order multiplexed OAM states and therefore cannot fully exploit the high-dimensional encoding capability of structured OAM combs.

In a new study published in Light: Science & Applications, researchers from Beijing Institute of Technology developed a hybrid intelligent strategy that enables high-dimensional OAM-comb multicasting through single-shot phase-only holography. By integrating deep-learning-assisted phase generation with physics-guided diffraction-order manipulation, the proposed framework simultaneously controls OAM modal distributions and spatial diffraction channels within a single hologram.

The proposed system expands the communication dimensionality through two complementary routes. First, multiple diffraction orders are used to establish parallel multicasting channels for one-to-many transmission. Second, each channel employs structured OAM combs as high-dimensional symbols, significantly increasing the encoding capacity within a single spatial channel. Through this strategy, the researchers experimentally demonstrated 4-, 6-, and 8-channel OAM-comb multicasting systems, with each channel supporting 1024-ary OAM shift keying.

To improve the transmission security, the team further introduced a mixed encoding protocol that combines unary and binary encoding within a unified OAM-comb framework. A designated OAM mode functions as a discriminant bit to dynamically determine the decoding branch. This hierarchical encoding strategy enables high-capacity information mapping while maintaining reliable symbol discrimination under multi-channel transmission conditions.

The researchers experimentally implemented a six-channel encrypted image transmission system. Different image contents, including institutional logos, natural scenes, flowers, and animal photographs, were independently encoded into six OAM-comb multicast channels and transmitted simultaneously through a single phase-only hologram. At the receiver side, a Damman-vortex-grating decoding module spatially separated the transmitted OAM-comb channels for independent detection and decoding.

The reconstructed images exhibited high fidelity with negligible inter-channel crosstalk. All six channels achieved bit-error rates below 7×10⁻⁵ during real-time transmission. In addition, decoding attempts using only conventional binary or unary strategies failed to recover the transmitted information, demonstrating the enhanced security enabled by the mixed encoding proposal. Importantly, the entire system operates through programmable phase-only modulation without requiring additional bulky optical components, highlighting its strong engineering potential for practical deployment.

In summary, this work establishes a scalable architecture for high-dimensional OAM communications and opens new opportunities for ultra-capacity optical networking, high-dimensional photonics, and secure optical communications.

---

---