Diffusion in translucent media

TL;DR

This paper demonstrates that the scaling of transmission and eigenchannel intensity profiles in translucent media resemble those in opaque media, revealing unexpected similarities in wave transport behavior across different regimes.

Contribution

It shows that wave transport in translucent media follows similar scaling laws as in opaque media, challenging existing diffusion theory assumptions.

Findings

Transmission scaling is similar in translucent and opaque media.

Eigenchannel intensity profiles follow the same form across regimes.

Suppressed optical and ultrasonic delay times are explained by these similarities.

Abstract

Diffusion is the result of repeated random scattering. It governs a wide range of phenomena from Brownian motion, to heat flow through window panes, neutron flux in fuel rods, dispersion of light in human tissue, and electronic conduction. It is universally acknowledged that the diffusion approach to describing wave transport fails in translucent samples thinner than the distance between scattering events such as are encountered in meteorology, astronomy, biomedicine and communications. Here we show in optical measurements and numerical simulations that the scaling of transmission and the intensity profiles of transmission eigenchannels have the same form in translucent as in opaque media. Paradoxically, the similarities in transport across translucent and opaque samples explain the puzzling observations of suppressed optical and ultrasonic delay times relative to predictions of diffusion theory well into the diffusive regime.