Simultaneously sorting vector vortex beams of 120 modes

Abstract: Polarization (P), angular index (l), and radius index (p) are three independent degrees of freedom (DoFs) of vector vortex beams, which have been widely used in optical communications, quantum optics, information processing, etc. Although the sorting of one DoF can be achieved efficiently, it is still a great challenge to sort all these DoFs simultaneously in a compact and efficient way. Here, we propose a beam sorter to deal with all these three DoFs simultaneously by using a diffractive deep neural network (D$<sup>2$NN) and experimentally demonstrated the robust sorting of 120 Laguerre-Gaussian (LG) modes using a compact D$<sup>2$NN formed by one spatial light modulator and one mirror only. The proposed beam sorter demonstrates the great potential of D$<sup>2$NN in optical field manipulation and will benefit the diverse applications of vector vortex beams.