An effective medium approach to the dynamic optical response of a graded index plasmonic nanoparticle

The optical response of graded index spherical particles is studied using an effective medium approach, where the homogenization of the graded particle is achieved by using a static effective dielectric function available in the literature. Full wave calculation using the standard Mie theory for this "homogenized system" shows that for a plasmonic particle, such an approximation can lead to highly-accurate results compared to the exact ones, especially for slowly and smoothly varying index profiles. An illustration is provided via an application of this method to the design of an optical cloak using a graded plasmonic coating based on the scattering cancelation scheme. This approach thus surpasses the various long-wavelength approximations currently available in the literature and provides an efficient numerical treatment of light scattering from these inhomogeneous particles without having to solve directly the Maxwell's equations with spatially varying dielectric functions. * Corresponding author at [email protected] OCIS numbers: 160.2710, 260.2065, 260.2110, 290.2200, 290.4020