Strong coupling in an Au plasmonic antenna– SiO2 layer system: A hybrid-mode analysis

A detailed analysis of the optical response of a system accommodating several coupled modes is needed for the complete understanding of the strong coupling effect. In this paper, we report on the analysis of scattering cross-section spectra of Au antennas on a ${\mathrm{SiO}}_{2}$ layer on a Si substrate in the IR region. A classical model of coupled oscillators is used for determining the resonant energies, damping rates, and coupling strengths of four phonon polariton modes in the ${\mathrm{SiO}}_{2}$ layer coupled to a localized surface plasmon mode in a Au antenna. The calculated Hopfield mixing coefficients then show the contribution of the individual uncoupled modes to the hybrid modes of the coupled system.