# Plasmon lifetime enhancement in a bright-dark mode coupled system

## TL;DR

This paper investigates how coupling bright and dark plasmon modes in metallic nanoparticles can significantly enhance plasmon lifetime, with implications for nanophotonics and quantum emitter applications.

## Contribution

It demonstrates, through exact 3D Maxwell simulations, that optimal bright-dark mode coupling maximizes plasmon lifetime without precise nanostructure positioning.

## Key findings

- Lifetime of plasmons can be increased via dark mode coupling
- Maximum lifetime enhancement occurs at an optimal coupling point
- Precise nanostructure positioning is not necessary for enhancement

## Abstract

Metallic nanoparticles can localize the incident light to hotspots as plasmon oscillations, where the intensity can be increased up to four orders of magnitude. Even though the lifetime of plasmons are typically short, it can be increased via interactions with quantum emitters, e.g. spaser nano-lasers. However, molecules can bleach in days. Here, we study the lifetime enhancement of plasmon excitations due to the coupling with longer lifetime dark plasmon modes. Exact solutions of the 3D Maxwell equations, i.e. FDTD, demonstrates that the lifetime of the coupled system increases, as also predicted by a basic oscillator model. We report an optimum bright-dark plasmon mode coupling, where lifetime enhancement becomes maximum, and show that no precise positioning of the nanostructures is required to obtain enhanced lifetime.