Photonic nanojet calculations in layered radially inhomogeneous micrometer-sized spherical particles

A photonic nanojet (PNJ) corresponds to the specific highly localized spatial region of electromagnetic near-field distribution in the vicinity of a transparent micrometer-sized particle illuminated by a light wave. Here we consider dielectric spherical composite particles consisting of a core and several concentric shells having different refractive indices. The longitudinal and latitudinal sizes of a PNJ and its peak intensity depending on the optical contrast variation of shells are numerically investigated. We show that by properly changing the refractive indices of neighboring shells, it is possible to manipulate the PNJ shape and, in particular, extend its longitudinal size or increase its peak intensity.