Nonlinear nanopolaritonics: finite-difference time-domain Maxwell-Schrödinger simulation of molecule-assisted plasmon transfer.

The effect of nonlinear excitations of a nearby two-state dipolar molecule on plasmon transfer across a pair of spherical gold nanoparticles is studied numerically using a split field finite-difference time-domain Maxwell-Schrödinger approach [K. Lopata and D. Neuhauser, J. Chem. Phys. 130, 104707 (2009)]. It is observed in the linear response regime that the molecule has a drastic effect on plasmon transfer; specifically, there is a Fano-type resonance that serves to scatter localized plasmons from x-polarization to y-polarization. With increasing nonlinearity of the molecular excitation, the scattering effect saturates due to the limited capacity of the molecule to absorb and radiate energy once the excited and ground states are equally populated.