19 research outputs found
Signatures of strong coupling on nanoparticles Revealing absorption anticrossing by tuning the dielectric environment
Strongly coupled plasmon-exciton systems offer promising applications in
nanooptics. The classification of the coupling regime is currently debated both
from experimental and theoretical perspectives. We present a method to
unambiguously identify strong coupling in plasmon-exciton core-shell
nanoparticles by measuring true absorption spectra of the system. We
investigate the coupling of excitons in J-aggregates to the localized surface
plasmon polaritons on gold nanospheres and nanorods by fine-tuning the plasmon
resonance via layer-by-layer deposition of polyelectrolytes. While both
structures show a characteristic anticrossing in extinction and scattering
experiments, the careful assessment of the systems' light absorption reveals
that strong coupling of the plasmon to the exciton is only present in the
nanorod system. In a phenomenological model of two classical coupled
oscillators, intermediate coupling strengths split up only the resonance
frequency of the light-driven oscillator, while the other one still dissipates
energy at its original frequency. Only in the strong-coupling limit, both
oscillators split up the frequencies at which they dissipate energy,
qualitatively explaining our experimental finding