Observing Nonlinear Plasmon-Exciton Coupling for Enhanced Harmonic Generation

Nonlinear plasmonics holds great promise to create subwavelength coherent light sources. Coupling plasmons to excitons further boosts the nonlinear efficiency by utilizing the field localization of plasmons and large nonlinear susceptibility of dielectrics. The increase of nonlinear efficiency is commonly interpreted by a phenomenological field enhancement. A detailed microscopic mechanism of plasmon-exciton coupling and their field dynamics, which are fundamentally important to the understanding and rational design of such coupled systems, remains to be uncovered. In particular, this involves nonlinear plasmon-exciton coupling.