Experimental synthesis of orbital angular momentum flux density-preserving random structured vortex beams

Optical coherence plays a crucial role in controlling the orbital angular momentum (OAM) characteristics of random structured beams. However, due to low spatial coherence, the OAM flux density distribution in traditional low-coherence vortex beams often fails to remain stable during propagation, leading to significant degradation with distance. In this work, we propose and experimentally demonstrate an OAM-preserving random structured vortex beam based on spatially varying correlation modulation. Both theoretical and experimental results show that, under the influence of spatially varying correlation, the beam maintains its hollow zero-intensity characteristic caused by phase singularity throughout propagation, while preserving the spatial distribution of OAM flux density without degradation. This approach provides an effective method for constructing robust random structured vortex beams with OAM preservation, offering significant potential for applications in free-space optical communication.