2, Institut des Sciences Moleculaires - UMR 5255 CNRS, Talence, , France
3, Institut Langevin, ESPCI - CNRS UMR7587, Paris, , France
Disordered optical media are ubiquitous in nature, and a proper description of light propagation in such materials is crucial for a number of applications ranging from the characterization of these materials to the fabrication of new types of lasers .
We have shown earlier that light diffusion is critically dependent on the finite lateral size in disordered meso-macroporous materials with a cylindrical shape . In a second step, we showed the light diffusion behaviour in (HIPE)-based isodense polystyrene foams , a study which strongly motivated further investigations into the limits of validity of the observed scalability between the light transport mean free path and the pore sizes as the scattering strength of the system increases.
Recently, we have numerically predicted and experimentally shown the coexistence and competition of random lasing (RL) and stimulated Raman scattering (SRS) in active disordered random media . We developed a simple model which includes both mechanisms coupled through diffusion equations. We found that the prevalence of a nonlinear mechanism over the other is determined by the degree of scattering. The competition was explained in terms of disorder-dependent pump depletion and fluorescence saturation.
In this talk, we will provide a short review of the salient features of these effects. Then, based on our experience in the realization and characterization of 3-dimensional disordered porous materials, we will show that the infiltration of molecules or nano-crystals with second order (Hyper Rayleigh Scattering, Second Harmonic Generation) nonlinear optical properties in such disordered 3D porous materials lead to a nonlinear enhancement factor. The effect of coherence in such processes will be discussed. These preliminary results are well accounted for by numerical FEM simulations, which will also be presented.
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