Berlin 2005 – scientific programme

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DY: Dynamik und Statistische Physik

DY 34: Poster

DY 34.56: Poster

Monday, March 7, 2005, 15:30–18:00, Poster TU D

Light Transport in Foams — •Michael Schmiedeberg and Holger Stark — Universitaet Konstanz, Fachbereich Physik, M621, 78457 Konstanz

Recent light-scattering experiments on foams suggest that the light transport is diffusive. This means that single photons can be considered as random walkers. In our studies, we construct two-dimensional Voronoi foams and replace the edges of the cells by channels of finite width to represent the liquid films. Based on geometrical ray optics, we then investigate how light propagates through a foam by using random walk theories and simulations.

Experiments by Durian et al. show that light possesses a higher probability to propagate in the liquid films. To model the extrem case of such a photon channeling, we first assume that all photons are completely reflected at each liquid-air interface so that they only move within the films. Then we relax this constraint and introduce reflection and transmission probabilities according to Fresnel’s formulas. In both cases, simulations of the photons’ random walk in a perfect honeycomb structure reveal superdiffusive behavior which we also explain within the theory of Lévy walks. In disordered lattices, light transport is, however, diffusive and depends strongly on the amount of disorder.