Advances in Mode (De)Multiplexing Technologies via Circularly Symmetric Structured Light Beams

The exponentially escalating global bandwidth demands have propelled mode-division multiplexing technologies as critical enablers for enlarging optical communication capacity. Leveraging spatially orthogonal photonic eigenmodes of circularly symmetric structured light beams, such as orbital angular momentum (OAM) and cylindrical vector beam (CVB) modes, enables the parallel multiplexing of large-scale digital signals within a single physical channel. This thus significantly expands data transmission density and advances next-generation optical communications and networks forward. This review aims to achieve a comprehensive overview of mode (de)multiplexing technologies using OAM/CVB modes, which are mainly categorized into beam splitter combinations, multiorder diffractive gratings, optical coordinate transformations, angular dispersion lenses, multilayer cascaded modulations, and multidimensional mode hybrid (de)multiplexing. Insights into their current capabilities and limitations are included. We conclude by analyzing the challenges and prospects of this promising field, paving the way for future developments and innovations.