Multipole Born series approach to light scattering by Mie-resonant nanoparticle structures

Optical response of Mie-resonant nanoparticles can be modeled either by full-wave numerical simulations or by the widely used analytical coupled multipole method (CMM). However, an analytical solution in the framework of CMM can be obtained only in a limited number of cases. In this paper, a modification of the CMM in the framework of the Born series and its applicability for the simulation of light scattering by finite nanosphere structures, maintaining both dipole and quadrupole resonances, are investigated. The Born approximation simplifies an analytical analysis of various systems and helps shed light on physical processes ongoing in that systems. Using Mie theory and Green’s functions approach, we analytically formulate the rigorous coupled dipole-quadrupole equations and their solution in the different-order Born approximations. We analyze in detail the resonant scattering by dielectric nanosphere structures such as dimer and ring to obtain the convergence conditions of the Born series and investigate the influence of the physical characteristics such as absorption in particles, type of multipole resonance, and geometry of ensemble on the convergence of Born series and its accuracy.