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Microscale Disordered Optofluidics
1  Universit√© Paris-Est

Abstract:

Disordered optics is a fascinating area, yet not fully understood, as it increasingly attracts interest due to the virtues of multiple scattering of light in diffusive materials and their numerous applications to imaging through opaque media, to spectroscopy as well as more fundamental optical transport properties including Anderson localization. Among the various kinds of disordered media, Black Silicon is a randomly micro-structured surface exhibiting several outstanding optical and wetting properties, which makes it increasingly used in various applications that will be discussed. On the other hand, complex fluids and especially colloidal suspensions have the specific feature of the time-dependence of the disorder; even in the static equilibrium regime of no flow, complex fluids exhibit Brownian motion of the embedded particles leading to an additional dimension to the disorder. The heterogeneous nature of complex fluids induces specific behavior at the microscale as well as collective effects at larger scales. This holds true not only regarding rheology but also in the optical domain, where one can define an effective refraction index in a medium subject to microscale effects of light scattering. Furthermore, it is also intuitive to think of a possible time-dependence of those properties. This poses the question of the most appropriate length scale and time scale to perform measurements in such media.

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