Dipolar analysis of substrated particles using a far-field response method

Abstract

The presence of a substrate, when working with nanoparticles, is essential in many applications, like optical nanoantennas, solar cells, and sensing. Understanding the effects of substrates upon the nanoparticles is, therefore, important, as the substrates typically affect the resonance behaviors of particles, as well as the interactions between their electric and magnetic resonances. In order to better understand the impacts of substrates in practical applications with nanoparticles, this paper presents a semianalytical method to calculate the polarizability tensors of individual nanoparticles located on dielectric substrates. This approach is based on a sampling of the scattered far-field responses to plane-wave illuminations from structures. By using scattered far fields, the induced electric and magnetic dipole moments are calculated at the geometrical center of a particle. Then, using these dipole moments, the individual polarizability tensors of the substrated particle are calculated. To show the accuracy of the proposed method, the numerical results of different particles on a substrate are compared to two other approaches, and the results are shown to be in good agreement with these approaches. Moreover, the effect of the refractive index of the substrate and the geometric characteristics of the particle on the substrate-induced bianisotropy are also investigated. The proposed method clearly demonstrates how a particle without any bianisotropic interaction in free space can possess this property in the presence of a dielectric substrate.