Enhancement of Nonlinear Refractive Index due to Surface Plasmon Polaritons in Plasmonic Nanohybrids

A theoretical model for the enhancement of the one-photon nonlinear refractive index (n2) has been developed for plasmonic nanohybrids doped with interacting metallic nanoparticles and quantum emitters. The one-photon nonlinear refractive index depends on the third-order susceptibility, and it is calculated using the quantum density matrix method. Analytical expressions for the one-photon nonlinear refractive index are calculated in the presence of surface plasmon polaritons (SPPs) and dipole–dipole interaction (DDI) polaritons. These expressions provide a foundation for designing new experiments and developing plasmonic devices. We predict a significant enhancement of the refractive index of the quantum emitters arising from the additional contribution of SPP polaritons. This finding may enable the design of plasmonic nanosensors. We compare our theoretical results with experimental measurements of the Kerr emission coefficient and find strong agreement. Furthermore, we predict that the refractive index enhancement can be switched on or off through DDI coupling. This can be used to make plasmonic nanoswitches.