Fiber-Integrated Hybrid Fresnel Lens for Orbital Angular Momentum Demultiplexing

In recent years, the potential of orbital angular momentum (OAM) (de)multiplexing to greatly increase the capacity of optical communications has attracted tremendous attention worldwide. Despite the extensive research on various OAM demultiplexing techniques, there is still a need for a compact, efficient, and fiber-integrated OAM demultiplexer. Our solution involves designing a hybrid Fresnel lens that combines angular and radial lenses, which is then integrated onto the end face of a few-mode fiber using two-photon lithography technology. The resulting all-fiber OAM integrated demultiplexing device enables the demultiplexing of OAM beams transmitted through fiber using only one lens, with a demultiplexing efficiency of over 53%. This scheme provides a promising boost for promoting OAM demultiplexing technology based on optical fiber in the future.