Resonance fluorescence beyond the dipole approximation of a quantum dot in a plasmonic nanostructure

TL;DR

This study explores how the breakdown of the dipole approximation in quantum dots affects resonance fluorescence, revealing the significant role of quadrupole moments and enabling control over spectral features for nanophotonic applications.

Contribution

It demonstrates the impact of mesoscopic effects beyond the dipole approximation on quantum dot fluorescence near plasmonic structures, including spectral switching and correlation properties.

Findings

Quadrupole contributions significantly influence fluorescence spectra.

Manipulating QD orientation switches the spectrum between Mollow triplet and single peak.

Fluorescence antibunching varies with radiation regime.

Abstract

The mesoscopic characteristics of a quantum dot (QD), which make the dipole approximation (DA) break down, provide a new dimension to manipulate light-matter interaction [M. L. Andersen et al., Nat. Phys. 7, 215 (2011)]. Here we investigate the power spectrum and the second-order correlation property of the fluorescence from a resonantly driven QD placed on a planar metal. It is revealed that due to the pronounced QD spatial extension and the dramatic variation of the triggered surface plasmon near the metal, the fluorescence has a notable contribution from the quadrupole moment. The {\pi}-rotation symmetry of the fluorescence to the QD orientation under the DA is broken. By manipulating the QD orientation and quadrupole moment, the spectrum can be switched between the Mollow triplet and a single peak, and the fluorescence characterized by the antibunching in the second-order correlation function can be changed from the weak to the strong radiation regime. Our result is instructive for utilizing the unique mesoscopic effects to develop nanophotonic devices.