Light-exciton interaction can be highly modified when excitons strongly couples to a plasmonic nanocavity, giving rise to a hybrid plasmon-exciton state. In this regime the energy exchange rate between the plasmon and exciton exceeds any other decay process and lead to the splitting in both the dark-field scattering and fluorescence spectra of the structure. Here we used colloidal assembly method to fabricate sanwiched Au-quantum dot-Au structures to demonstrate the impact of mode volume of the plasmonic cavity on the coupling strength. We carefully selected the quantum dot and the gold nanoparticles so that the fluorescence of the exciton aligns with transverse mode of the gold nanoparticle dimer. With decreased gap size of the gold dimer, we observed the splitting effect of both dark-filed scattering and fluorescence spectra from individual hyrid structures. Transmission electron microscopy was applied to obtain the morphology of the structures that correlates with their optical spectra further. The correlated study confirms the origin of the peak splitting is due to the strong plasmon-exciton coupling.

Strong plasmon-exciton coupling in collodially assembled Au quantum-dot structures

2019 Spring National Meeting

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