Efficient Angular Separation of the Dense Orbital Angular Momentum of Light

Sorting orbital angular momentum (OAM) of light is crucial for the success of optical multiplexing systems. Recently, research on OAM sorting has achieved angular separation via photonic momentum transformation. Nevertheless, efficiently sorting dense OAM modes in angular directions still remains challenging. Here, we present a method to implement efficient angular separation of dense OAM modes. A hybrid Fresnel lens in the angular domain and radial domain is used in combination with an OAM multiplier to achieve better mode discrimination and reduced mode overlap. The favorable performance is demonstrated in both simulation and experiment. Our method may find great potential in future optical telecommunications, optical manipulation, and quantum systems.