Abstract

Orbital Angular Momentum (OAM) of light has emerged as a powerful and versatile degree of freedom, offering a new paradigm for enhancing both the capacity and security of optical communication systems. Unlike traditional methods that rely on polarization or wavelength division, OAM exploits the spatial structure of light beams, which can carry theoretically unbounded orthogonal modes distinguished by their helical phase fronts. This unique property enables the simultaneous transmission of multiple independent data streams over a single channel, significantly increasing spectral efficiency and data throughput in classical communication networks. In classical regimes, OAM-based multiplexing and demultiplexing techniques allow for the scaling of communication systems to meet the growing demands of high-speed data transfer. Research has demonstrated the successful transmission of terabit-per-second data rates using OAM beams over free-space and fiber-optic links, though challenges such as atmospheric turbulence, mode dispersion, and alignment sensitivity remain areas of active development. In the quantum communication domain, OAM states offer a high-dimensional Hilbert space that surpasses the binary encoding of traditional qubits, enabling the use of qudits for quantum information protocols. This dimensional enhancement can increase the channel capacity, improve noise resilience, and enhance the security of quantum key distribution (QKD) systems. OAM also plays a critical role in facilitating complex quantum phenomena such as high-dimensional entanglement, quantum teleportation, and quantum state tomography. Recent advances in OAM photon sources, spatial light modulators, and detection schemes have paved the way for experimental demonstrations of quantum communication using OAM-encoded photons. We explore a comprehensive overview of the theoretical foundations of OAM, the current state-of-the-art in its generation and detection techniques, and its integration into classical and quantum communication frameworks. Special attention is given to the development of hybrid systems that combine OAM with other degrees of freedom, such as polarization or time-bin encoding, to further enhance communication robustness and scalability. The convergence of classical and quantum technologies through OAM is expected to play a vital role in the evolution of secure, high-capacity communication infrastructures, including future quantum internet architectures and space-based optical links. Despite technical challenges, the ongoing research and rapid progress in this field hold significant promise for transforming the landscape of optical communication.

Biography

Satyendra Kumar Mishra received his Ph.D. in Physics from IIT Delhi in 2015, following degrees in Physics and Nanotechnology from DDU Gorakhpur University and Jamia Millia Islamia. He has held postdoctoral and research positions at City University of Hong Kong, Texas A&M University, Baylor University, ÉTS Montreal, and Laval University. Currently, he is a Senior Researcher at the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Barcelona, Spain. He has authored over 120 journal and conference publications and holds one pending patent. His research focuses on quantum communication, quantum sensors, optical communication, vortex beams, fiber/waveguide sensors, photodetectors, and metasurfaces. He also serves as an Editor for IEEE Sensors Journal, Scientific Reports, and Light: Science & Applications – Discover.