Orbital angular momentum mode sorting by wavefront shaping with customizable optical phase conjugation through a diffuser

Light field control through a diffuser using feedback wavefront shaping (WS) is an emerging method for sorting in orbital angular momentum (OAM) multiplexed communications. However, the feedback iterative optimization of the wavefront shaper converges slowly, reducing the real-time capability. Herein, we developed a WS scheme using a diffuser with customizable optical phase conjugation (COPC) for arbitrary OAM light control and mode sorting without iteration. The numerical and experimental results showed that the multiplexed OAM mode can be sorted into predefined spatial positions. Moreover, we found that the OAM mode with a larger topological charge |l| has stronger focusing, i.e., higher transmittance through the diffuser. Furthermore, we demonstrated that two, four, six, and eight modes can be sorted beyond 0.99, 0.93, 0.87 and 0.79 detection probabilities in the experiment.