Approximate Methods for Simulating Optical Properties of Plasmonic Nanoparticle Assemblies

Abstract

Simulating optical responses of plasmonic nanoparticle assemblies is a crucial milestone for advancing the design and optimization of optical metamaterials and photonic devices. Since optical responses are highly dependent on light frequencies sampled on particle structures, simulations often iterate its calculation on small increments of frequencies to preserve high resolution for the resulting spectra, leading to a high computational cost. In this thesis, we introduce the Kramers-Kronig resonance frequency (KK-res) approximation. KK-res only requires two particle dipole calculations at low- and high-frequency limit, rather than particle dipoles at each frequency, to estimate the full extinction spectra of large particle configurations ($N>10^4$). This allows KK-res to gain an order-of-magnitude computation time improvement comparing to other coarse-grained mutual dipoles methods. Several experimental studies were also simulated with KK-res to gauge the accuracy and utility under conditions like various anisotropic structures and dielectric models.