Metasurfaces for Applications of Multi-Dimensional Orbital Angular Momentum Mode (De)multiplexing

Orbital angular momentum (OAM) mode, as an emerging physical dimension for optical (de)multiplexing, offers unprecedented potential to enhance communication capacity density by synergistically operating with conventional domains such as polarization and wavelength. Metasurfaces, with their subwavelength configurability and multi-parameter manipulation capabilities, serve as powerful platforms for engineering multi-dimensional OAM modes. They bring revolutionary advantages – including increased parallel processing dimensions, improved light-field modulation efficiency, and system miniaturization – beyond those achievable with conventional optical components in multi-dimensional OAM mode treatment. This chapter dissects metasurface-enabled strategies for hybrid multiplexing/demultiplexing in three multi-physical domain scenarios: OAM–polarization parallel processing using the expanded Pancharatnam–Berry phase for orthogonal linearly polarized Dammann-vortex interactions; OAM–wavelength parallel manipulation utilizing a dispersion-engineered multi-foci transformation strategy implemented in broadband meta-atoms; and tri-domain (OAM–polarization–wavelength) parallel (de)multiplexing realized through spin-decoupled cascaded phase modulation on a five-layer diffractive meta-platform. For each scenario, the fundamental principles, design methodologies, optical demonstrations, and performance trade-offs are discussed. The chapter highlights the pivotal role that metasurfaces are poised to play in shaping the development of next-generation high-speed, large-capacity all-optical communication networks.