Interaction of optical Whispering Gallery Modes with the surface layer of evaporating droplet of suspension

- Rapid increase of light scattering was found in drying droplets of suspension.
- Formation of surface layer of inclusions was presumed.
- Interaction of surface inclusions with Whispering Gallery Modes was identified.
- Number, mean distance, order parameter and refractive index of surface were found.

We investigate scattering of light on micro droplets of suspensions of 100-nm and 225-nm-radius dielectric spheres in glycols. Rapid increase of scattered light intensities accompanied by light depolarisation was observed on presumed formation of the surface layer of inclusions. We determined the effective refractive index of the droplet (surface) evolving during the formation of the surface layer of inclusions. We present a model enabling identification of interaction of surface structures of inclusions with Whispering Gallery Modes of the droplet. It seems possible to exploit the evaporation of micro droplets of suspension as a method of production of composite objects with very specific indices of refraction.