Temperature-controlled light diffusion in random media

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Abstract
We have studied diffusion of light in a disordered medium of which the scattering strength could be tuned via temperature. Such a tunable disordered system was realized by infiltrating a macro porous glass with a liquid crystal. In particular, we have measured the diffusion constant in time-resolved transmission measurements on macroporous silica glass infiltrated with liquid crystal 8CB. The measured temperature dependence of the diffusion constant can be understood qualitatively from the behavior of liquid crystals in confined geometries, and provides an alternative method to resolve liquid crystal phase transitions in such structures. The observed effect allows for control of the scattering strength in multiple light scattering studies and can be regarded as the optical counterpart of negative temperature coefficient resistivity in electronics.