Vectorial near-field coupling

TL;DR

This paper demonstrates a novel spectroscopy technique to analyze vectorial near-field coupling between dipoles at nanometer resolution, revealing how orientation and distance affect optical interactions in nanosystems.

Contribution

It introduces plasmonic nanofocusing spectroscopy for high-resolution analysis of vectorial near-field interactions, enabling detailed study of mode coupling and resonance shifts.

Findings

Resolved mode couplings and resonance energy shifts.

Demonstrated control of optical properties via dipolar alignment.

Showed dependence of interactions on vectorial components of near-fields.

Abstract

The coherent exchange of optical near fields between two neighboring dipoles plays an essential role for the optical properties, quantum dynamics and thus for the function of many naturally occurring and artificial nanosystems. These interactions are inherently short-ranged, extending over a few nanometers only, and depend sensitively on relative orientation, detuning and dephasing, i.e., on the vectorial properties of the coupled dipolar near fields. This makes it challenging to analyze them experimentally. Here, we introduce plasmonic nanofocusing spectroscopy to record coherent light scattering spectra with 5-nm spatial resolution from a small dipole antenna, excited solely by evanescent fields and coupled to plasmon resonances in a single gold nanorod. We resolve mode couplings, resonance energy shifts and Purcell effects as a function of dipole distance and relative orientation, and show how they arise from different vectorial components of the interacting optical near-fields. Our results pave the way for using dipolar alignment to control the optical properties and function of nanoscale systems.