Fractional Orbital Angular Momentum Sorting Using Wind Spiral Transformation.

Orbital angular momentum (OAM) mode sorting is a crucial component of the optical multiplexing systems based on the optical vortex beam carrying OAM. However, the number of sortable integer-order OAM states remains limited. Herein, we propose a general spiral transformation, that is, wind spiral transformation, to conduct sortable fractional-order OAM states to solve the existing drawback. By transforming a fractional-order OAM mode into a superposition of integer-order OAM states, the sorting capacity of OAM mode is significantly extended, where the proposed method is suitable for integer and fractional OAM mode sorting. Further, the proposed scheme is applied to image encoding and decoding, resulting in good image reconstruction and unlocking a scalable paradigm for high-dimensional information encoding and decoding. This proposed sorting method shows great potential for implementing highly confidential data storage systems, which may encourage further applications in classical and quantum regimes.