Figure 5

Ballistic, sub-diffusive, and diffusive scattering regimes for photons incident on a 3 cm length enclosure containing scattering media. The mean free path of a photon in the medium is equal to the reciprocal of the reduced scattering coefficient μ_sʹ. The center and edge of the formed waveguide in the suspension of red blood cells are within the sub-diffusive light scattering regime, wherein minimal information loss due to degradation of polarization and coherence is expected. For reduced scattering coefficients less than 1/30 = 0.033 mm⁻¹, the mean free path becomes larger than the length of the container (30 mm), so photon transport can be approximated as ballistic. As μ_sʹ increases sufficiently to allow more than ~ 10 scattering events within the container (μ_sʹ  ~ 0.4–0.5 mm⁻¹), the transport of light begins to approach the diffusive regime (as is the case with biological tissue, which typically has μ_sʹ  ~ 0.8–1.5 mm⁻¹), wherein a sufficient number of scattering events occur that the initial polarization and coherence states of the light are degraded.