Electromagnetically Coupled Au Nanoparticles

The current intense interest in the properties of gold nanoparticles for their applications in antenna design, optical sensing, optical quality control, biotechnology and medical diagnostics is currently based on their resonantly enhanced scattering properties. When two nanoparticles are put close enough, it results in novel coupling induced optical properties, which is not possible to investigate with numerical simulation algorithms, developed for investigation of single particle. In this work the algorithm was developed to investigate dimer of nanoparticles. It was taken into account that two coupled nanoparticles may form a heretodimer, namely dimer of particles of different size, different shape, different materials. In addition, assuming that position and orientation of each nanoparticle are fixed, it was taken into account that parameters of the light source, such as source position, an excitation wavelength and a direction of illumination can vary. The spectral Boundary Integral Equation method was used, that is known to be a very useful and versatile tool to solve electromagnetic transmission problems. While this method includes analytical regularization based on singularity divison, it was found that regularization of those kernels, which are responsible for coupling of the nanoparticles, is not needed because they do not contain singularities. Developed algorithm allows calculations of scattering characteristics for coupled Au nanoparticles for various wavelength of their illumination. The set of numerical experiments lead to development of mathematical relations used as design rules, which qualitatively describe the plasmonic coupling between dimmers and asymmetric heterodimers as a function of orientation and interparticle distance.