Changes in the degree of polarization of random electromagnetic GSM vortex beams in biological tissues

Based on the Huygens-Fresnel principle, the analytic expressions of the cross-spectral density matrix elements of the random electromagnetic Gaussian Schell model (GSM) vortex beams in biological tissues are derived, and used to study the changes in the on-axis degree of polarization P(0, 0, z), one point degree of polarization P(ρ, ρ, z) and two points (generalized) degree of polarization P(0, ρ, z) of random electromagnetic GSM vortex beams. The results show that with the increment of the propagation distance z, the bigger Cn2 is, the earlier appearance of the inflexion points in P(0, 0, z) and P(ρ, ρ, z) are, but the changes in P(0, ρ, z) are related to the propagation distance. The smaller σxy is, the greater σyy is, the more smooth the change curves of P(0, 0, z), P(ρ, ρ, z) and P(0, ρ, z) are. Besides, the difference values between σxx and σyy also influence the changes in P(0, 0, z), P(ρ, ρ, z) and P(0, ρ, z). On the same conditions, the changes in P(0, ρ, z) are more complicate than those in P(ρ, ρ, z), and the changes in P(ρ, ρ, z) are more complex than those in P(0, 0, z).