title: Optical analysis of nanoparticles via enhanced backscattering facilitated by 3-D photonic nanojets.
abstract: We report the phenomenon of ultra-enhanced backscattering of visible light by nanoparticles facilitated by the 3-D photonic nanojet - a sub-diffraction light beam appearing at the shadow side of a plane-waveilluminated dielectric microsphere. Our rigorous numerical simulations show that backscattering intensity of nanoparticles can be enhanced up to eight orders of magnitude when locating in the nanojet. As a result, the enhanced backscattering from a nanoparticle with diameter on the order of 10 nm is well above the background signal generated by the dielectric microsphere itself. We also report that nanojet-enhanced backscattering is extremely sensitive to the size of the nanoparticle, permitting in principle resolving sub-nanometer size differences using visible light. Finally, we show how the position of a nanoparticle could be determined with subdiffractional accuracy by recording the angular distribution of the backscattered light. These properties of photonic nanojets promise to make this phenomenon a useful tool for optically detecting, differentiating, and sorting nanoparticles.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen
authors.forename: Allen
authors.initials: A
authors.lastname: Taflove
authors.forename: Vadim
authors.initials: V
authors.lastname: Backman