Propagation Characteristics of Partially Coherent Pin-Like OAM Vortex Beams in Turbulent Biological tissues

This study examines the propagation characteristics of partially coherent pin-like optical vortex beams that carry orbital angular momentum (OAM) within turbulent biological tissues. The objective is to assess their potential for deep-tissue optical communication and imaging. By employing the OAM probability-density diffraction integral and the Rytov approximation, we derive analytical expressions that describe the evolution of the OAM mode spectrum, spiral spectrum, and channel capacity of PCPO vortex beams in inhomogeneous biological media, which are modeled using fractal-based turbulence power spectra. Numerical simulations are conducted for several representative tissues, including the upper dermis, deep dermis, liver parenchyma, and intestinal epithelium, to assess the impact of tissue heterogeneity parameters, spatial coherence length, and topological charge on beam stability. The findings indicate that the probability of OAM detection diminishes with propagation distance and increasing topological charge, whereas greater spatial coherence length and larger characteristic heterogene-ity length enhance channel capacity. Biological tissues with higher fractal dimension and lower correlation length exhibit more pronounced turbulence-induced degradation. When the coherence length exceeds approximately 10 µm, the detection probability becomes nearly invariant with distance, suggesting a regime of enhanced robustness. These results provide quantitative insights into the feasibility and limitations of employing partially coherent OAM beams for optical information transfer in biological tissues and offer theoretical guidance for the design of OAM-based biomedical photonic systems.