Superenhanced backscattering of light by nanoparticles.

We report a physical explanation for the phenomenon wherein the backscattering of light by dielectric particles of sizes between 100 and 1 nm is enhanced by 7-11 orders of magnitude. The phenomenon involves complex composite interactions between a dielectric microsphere and a nanoparticle positioned in close proximity to the microsphere. We provide both analytical and perturbation analyses that show that the enhanced backscattering intensity of a nanoparticle is proportional to the third power of its size parameter. Potential applications of this phenomenon include visible-light detection, characterization, and manipulation of particles as small as a few nanometers.