Plasmon mode excitation and photoluminescence enhancement on silver nanoring

TL;DR

This paper presents a laser-assisted fabrication method for silver nanorings that enhances photoluminescence through plasmon excitation, confirmed by experiments and simulations, with potential applications in nanophotonics.

Contribution

A simple, high-performance laser-assisted technique for fabricating silver nanorings with controllable dimensions and demonstrated photoluminescence enhancement due to plasmon modes.

Findings

Five-fold increase in Rhodamine 6G photoluminescence near nanorings

Shifted focal spot inside the nanoring observed

Confirmation of multipole plasmon modes via spectrum and simulations

Abstract

We demonstrate a simple and high-performance laser-assisted technique for silver nanoring fabrication, which includes the ablation of the Ag film by focused nanosecond pulses and subsequent reactive ion polishing. The nanoring diameter and thickness can be controlled by optimizing both the pulse energy and the metal film thickness at laser ablation step, while the subsequent reactive ion polishing provides the ability to fabricate the nanoring with desirable height. Scattering patterns of s-polarized collimated laser beam obliquely illuminating the nanoring demonstrate the focal spot inside the nanoring shifted from its center at a distance of ~ 0.57Rring. Five-fold enhancement of the photoluminescence signal from the Rhodamine 6G organic dye near the Ag nanoring was demonstrated. This enhancement was attributed to the increase of the electromagnetic field amplitude near the nanoring surface arising from excitation of the multipole plasmon modes traveling along the nanoring. This assumption was confirmed by dark-field back-scattering spectrum of the nanoring measured under white-light illumination, as well as by supporting finite-difference time-domain simulations.