Characterization of a circular optical nanoantenna by nonlinear photoemission electron microscopy

TL;DR

This paper investigates a circular plasmonic nanoantenna using nonlinear photoemission electron microscopy, revealing detailed resonance behaviors and plasmonic effects with high spatial resolution, supported by simulations and analytical models.

Contribution

It demonstrates the use of PEEM to analyze complex plasmonic nanoantenna resonances and propagating plasmons, advancing nanoscale optical characterization techniques.

Findings

High-resolution field profiles of antenna resonance for different polarizations

Detection of outward propagating Hankel plasmons excited by the structure

Excellent agreement between experimental results, simulations, and analytical models

Abstract

We report on the investigation of an advanced circular plasmonic nanoantenna under ultrafast excitation using nonlinear photoemission electron microscopy (PEEM) under near-normal incidence. The circular nanoantenna is enhanced in its performance by a supporting grating and milled out from a gold film. The considered antenna shows a sophisticated physical resonance behavior that is ideal to demonstrate the possibilities of PEEM for the experimental investigations of plasmonic effects on the nanoscale. Field profiles of the antenna resonance for both possible linear polarizations of the incident field are measured with high spatial resolution. In addition, outward propagating Hankel plasmons, which are also excited by the structure, are measured and analyzed. We compare our findings to measurements of an isolated plasmonic nanodisc resonator and scanning near-field optical microscopy (SNOM) measurements of both structures. All results are in very good agreement with numerical simulations as well as analytial models that are also discussed in our paper.