Near-field imaging of plasmonic nanopatch antennas with integrated semiconductor quantum dots

TL;DR

This study uses cathodoluminescence microscopy to analyze near-field plasmonic responses in nanopatch antennas with integrated quantum dots, revealing differences in Purcell enhancement between optical and electron-beam spectroscopies.

Contribution

It provides new insights into near-field plasmon-exciton interactions and compares optical and electron-beam spectroscopic techniques for hybrid nanostructures.

Findings

Significant Purcell enhancement observed in time-resolved photoluminescence.

Negligible Purcell enhancement detected in cathodoluminescence spectroscopy.

Differences explained by distinct selection rules for optical and electron-beam excitations.

Abstract

Plasmonic nanopatch antennas that incorporate dielectric gaps hundreds of picometers to several nanometers thick have drawn increasing attention over the past decade because they confine electromagnetic fields to grossly sub-diffraction limited volumes. Substantial control over the optical properties of excitons and color centers confined within these plasmonic cavities has already been demonstrated with far-field optical spectroscopies, but near-field optical spectroscopies are essential to an improved understanding of the plasmon-emitter interaction at the nanoscale. Here, we characterize the intensity and phase-resolved plasmonic response of isolated nanopatch antennas with cathodoluminescence microscopy. Further, we explore the distinction between optical and electron-beam spectroscopies of coupled plasmon-exciton heterostructures to identify constraints and opportunities for future nanoscale characterization and control of hybrid nanophotonic structures. While we observe substantial Purcell enhancement in time-resolved photoluminescence spectroscopies, negligible Purcell enhancement is observed in cathodoluminescence spectroscopies of hybrid nanophotonic structures. The substantial differences in measured Purcell enhancement for electron-beam and laser excitation can be understood as a result of the different selection rules for these complementary experiments. These results provide a fundamentally new understanding of near-field plasmon-exciton interactions in nanopatch antennas that is essential to myriad emerging quantum photonic devices.