Extinction Efficiency and Electromagnetic Fields of Isolated and Coupled Core-Shell Nanoparticles

Abstract

The study of metallic nanoparticles fed by optical fields has great interest in nanophotonics, for example in sensing devices. This paper presents a theoretical study of the interaction between electromagnetic waves and gold nanostructures with spherical geometries, which have a thin dielectric layer of silica. It is considered that the particle’s size is much smaller than the operating wavelength, characterizing the Rayleigh scattering regime. Using an analytical model through the Laplace equation, the interaction between an oscillating uniform electric field and a core-shell nanosphere is presented. Then, using a numerical model, the scattering of two interacting core-shell nanospheres is also analyzed, as a function of the distance between them. For the isolated particle case, the efficiency parameters of scattering, absorption and extinction cross sections were calculated and compared with experimental data of absorbance curves. The results were obtained in the range of wavelengths from 450nm to 750nm. Some conclusions about the range of validity of the model in functions of the particle’s dimensions are presented.