Characterization of a circular optical nanoantenna by nonlinear photoemission electron microscopy
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 behaviour 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 analysed. We compare our findings to measurements of an isolated plasmonic nanodisc resonator and scanning near-field optical microscopy measurements of both structures. All results are in very good agreement with numerical simulations as well as analytical models that are also discussed in our paper.
KeywordsGold Film Electric Field Component Total Electric Field Bragg Resonance Localize Plasmonic Resonance
We thank N. Asger Mortensen (DTU Denmark) for stimulating discussions and Focus GmbH (Germany) for the sketch of the PEEM in Fig. 2. Funding is acknowledged by Deutsche Forschungsgemeinschaft (DFG SPP 1391 Ultrafast Nanooptics), the Thuringian Ministry for Economy, Science and Digital Society (TMWWDG Pro-Exzellenz program), and the Carl Zeiss foundation.
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