Selective excitation of bright and dark plasmonic resonances of single gold nanorods

TL;DR

This paper demonstrates a method to selectively excite bright and dark plasmonic resonances in single gold nanorods using spatial phase-shaping of the excitation beam, enabling better control of near-field interactions.

Contribution

It introduces a novel approach of spatial phase-shaping to efficiently excite dark modes in gold nanorods, overcoming limitations of traditional far-field methods.

Findings

Selective excitation of bright and dark modes achieved

Two-photon luminescence used to identify mode symmetry

Fourier-space imaging analyzed angular distribution

Abstract

Plasmonic dark modes are pure near-field resonances since their dipole moments are vanishing in far field. These modes are particularly interesting to enhance nonlinear light-matter interaction at the nanometer scale because radiative losses are mitigated therefore increasing the intrinsic lifetime of the resonances. However, the excitation of dark modes by standard far field approaches is generally inefficient because the symmetry of the electromagnetic near-field distribution has a poor overlap with the excitation field. Here, we demonstrate the selective optical excitation of bright and dark plasmonic modes of single gold nanorods by spatial phase-shaping the excitation beam. Using two-photon luminescence measurements, we unambiguously identify the symmetry and the order of the emitting modes and analyze their angular distribution by Fourier-space imaging.