Séminaire de l'INPHYNI: Frank Scheffold (Fribourg)

 Visible light can be used to probe dense, complex media such as colloidal suspensions or compact sediments. In liquid samples, the temporal fluctuations contain information about the local viscoelastic environment, which is exploited using the DWS tracer bead microrheology scheme. Samples composed of monodisperse dielectric spheres of suitable size exhibit vivid structural colors in reflection. These colors depend only weakly on the viewing angle, making such materials attractive for applications in packaging, jewelry, art, and decoration. Both static and temporally resolved reflected light from biological tissue provide information about tissue composition and metabolism.
Here, we present new data and models to achieve a better understanding of how light interacts with disordered dielectrics. We analyze the influence of strong structural correlations when the refractive index contrast becomes sizable. We also examine the role of single and low-order multi-scattering on the reflected signal, considering the effects of absorption and polarization. We develop simple theoretical models that we compare with Monte Carlo simulations and exact multi-sphere T-matrix calculations (MSTM).