Fig. 1.

Sketch of the system and light trajectories. (A) Geometry of the 3D slab of length L investigated numerically using the RTE. ${\varphi }_{\mathrm{in}}$ is the incident flux and ${\varphi }_{\mathrm{out},\mathrm{R}}$ and ${\varphi }_{\mathrm{out},\mathrm{T}}$ are the reflected and transmitted fluxes, respectively (${\varphi }_{\mathrm{out}}={\varphi }_{\mathrm{out},\mathrm{R}}+{\varphi }_{\mathrm{out},\mathrm{T}}$). (B and C) Projections of light trajectories inside the system in the case of normal incidence illumination at a specific point on the system boundary (see inward arrow) for two optical thicknesses, (B) $b=10$ and (C) $b=0.59$.