  Structured light with customized complex topological pattern inspires diverse
classical and quantum investigations underpinned by accurate detection
techniques. However, the current detection schemes are limited to vortex beam
with simple phase singularity. The precise recognition of general structured
light with multiple singularities remains elusive. Here, we report a deep
learning (DL) framework that can unveil multi-singularity phase structures in
an end-to-end manner after feeding only two intensity patterns upon beam
propagation captured via a camera, thus unleashing intuitive information of
twisted photons. The DL toolbox can also acquire phases of Laguerre-Gaussian
(LG) modes with single singularity and other general phase objects likewise.
Leveraging this DL platform, a phase-based optical secret sharing (OSS)
protocol is proposed, which is based on a more general class of
multi-singularity modes than conventional LG beams. The OSS protocol features
strong security, wealthy state space and convenient intensity-based
measurements. This study opens new avenues for vortex beam communications,
laser mode analysis, microscopy, Bose-Einstein condensates characterization,
etc.
