Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit

TL;DR

This paper demonstrates vacuum Rabi splitting indicating strong coupling between a single quantum emitter and a plasmonic cavity, using silver bowtie structures with quantum dots, achieving near-strong coupling conditions.

Contribution

First experimental observation of vacuum Rabi splitting at the single quantum emitter level in a plasmonic cavity with detailed validation.

Findings

Observed vacuum Rabi splitting with a single quantum dot

Coupling rate up to 120 meV achieved

Validated results with electromagnetic calculations

Abstract

The strong interaction of individual quantum emitters with resonant cavities is of fundamental interest for understanding light matter interactions. Plasmonic cavities hold the promise of attaining the strong coupling regime even under ambient conditions and within subdiffraction volumes. Recent experiments revealed strong coupling between individual plasmonic structures and multiple organic molecules, but so far strong coupling at the limit of a single quantum emitter has not been reported. Here we demonstrate vacuum Rabi splitting, a manifestation of strong coupling, using silver bowtie plasmonic cavities loaded with semiconductor quantum dots (QDs). A transparency dip is observed in the scattering spectra of individual bowties with one to a few QDs, directly observed in their gaps. A coupling rate as high as 120 meV is registered even with a single QD, placing the bowtie-QD constructs close to the strong coupling regime. These observations are verified by polarization-dependent experiments and validated by electromagnetic calculations.