Direct Nano-Imaging of Light-Matter Interactions in Nanoscale Excitonic Emitters

TL;DR

This study uses near-field nano-spectroscopy to directly observe strong light-matter interactions and surface plasmon polariton propagation in nanoscale excitonic emitters on gold, revealing new insights into their electromagnetic behavior.

Contribution

It provides the first direct near-field imaging of light-matter interactions and plasmonic wave propagation in nanoscale excitonic emitters on a metal substrate.

Findings

Strong exciton-plasmon coupling observed.

Directional surface plasmon polariton propagation mapped.

Light confinement and emission can be tuned by dielectric environment.

Abstract

Strong light-matter interactions in localized nano-emitters when placed near metallic mirrors have been widely reported via spectroscopic studies in the optical far-field. Here, we report a near-field nano-spectroscopic study of the localized nanoscale emitters on a flat Au substrate. We observe strong-coupling of the excitonic dipoles in quasi 2-dimensional CdSe/CdxZnS1-xS nanoplatelets with gap mode plasmons formed between the Au tip and substrate. We also observe directional propagation on the Au substrate of surface plasmon polaritons launched from the excitons of the nanoplatelets as wave-like fringe patterns in the near-field photoluminescence maps. These fringe patterns were confirmed via extensive electromagnetic wave simulations to be standing-waves formed between the tip and the emitter on the substrate plane. We further report that both light confinement and the in-plane emission can be engineered by tuning the surrounding dielectric environment of the nanoplatelets. Our results lead to renewed understanding of in-plane, near-field electromagnetic signal transduction from the localized nano-emitters with profound implications in nano and quantum photonics as well as resonant optoelectronics.