Analysis of extinction spectra and near-field electromagnetic coupling regimes for plexcitonic nanoparticles in the coupled oscillator model

We have performed a theoretical analysis of the extinction spectra of light in hybrid plasmon–exciton nanosystems. Within the framework of the quasistatic approximation, an analytical formula is derived that explicitly defines the dependence of the effective cross section of light extinction by a system of coupled oscillators on their eigenfrequencies and damping constants as well as on the coupling constant and the frequency of the incident light. The theory has been applied to the analysis of light absorption by specific plasmon–exciton nanosystems. These systems consist of a spherical and rod-shaped metal core coated with an outer layer of an isotropic molecular aggregate of a dye. We have shown that the results of the work can be used for quantitative interpretation of the available experimental data on the light extinction spectra in the regimes of weak and strong plasmon–exciton coupling. Studying the effects of plasmon–exciton coupling is of particular interest for the development of hybrid nanowaveguides, highly sensitive photodetectors, and optical sensors.