Orbital Angular Momentum Flux Density in Partially Coherent Beams with Noncanonical Vortex Pairs

This paper investigates the propagation properties and orbital angular momentum (OAM) flux density distribution of partially coherent beams embedded with noncanonical vortex pairs in free space. Based on the generalized Huygens–Fresnel integral, an analytical model of the cross-spectral density (CSD) is derived. Numerical simulations are performed to analyze how key parameters—including off-axis distance, topological charge, noncanonical strength, and coherence length—affect the spatial structure and evolution of the OAM flux density. The results show that the OAM flux density transitions from a symmetric ring to a bifurcated lobe structure as the off-axis distance increases. Both topological charge and noncanonical strength significantly enhance the magnitude and alter the morphology of the OAM flux density. Furthermore, under noncanonical conditions, the coherence length modulates the rotational behavior and spatial extent of the OAM profile. These findings provide insights into the control of OAM in structured partially coherent beams and suggest potential applications in optical communications, particle manipulation, and beam shaping.