Study of the influence of geometrical structuration of materials on the effectiveness of light emission and light absorption processes

In this project, we want to understand the influence of the geometrical structure of materials on the effectiveness of light emission and light absorption processes. The colored appearance of an object originates from pigments (use of selective absorption), interferences (use of spatial variations of the refractive index), or fluorescence (use of selective emission). Most of time, a distinction is made between structural coloration and pigmentary coloration in considering these two mechanisms of different nature. Our approach is mainly inspired by natural samples (insects, birds and plants) for which their visual appearance is a combination of different filtering processes. In this context, the goal of the research is to develop numerical techniques able to evaluate quantitatively the diffuse reflectance of a photonic structure containing absorbing grains of undefined form or extended light sources. The validation of the techniques will be made on different natural specimens where an experimental confrontation is possible. We want to continue these studies by designing films optimizing the absorption or the emission for industrial applications (painting, textile dyeing, glasses,...) or artistic applications and to extend this knowledge to other frequency ranges.