Momentum-resolved electron energy loss spectroscopy for mapping the photonic density of states

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DOIResolve DOI: http://doi.org/10.1021/acsphotonics.7b00103
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TypeArticle
Journal titleACS Photonics
ISSN2330-4022
Volume4
Issue4
Pages10091014
Subjectband structure; electron energy loss spectroscopy (EELS); nonlocality; photonic density of states; plasmonics
AbstractStrong nanoscale light–matter interaction is often accompanied by ultraconfined photonic modes and large momentum polaritons existing far beyond the light cone. A direct probe of such phenomena is difficult due to the momentum mismatch of these modes with free space light, however, fast electron probes can reveal the fundamental quantum and spatially dispersive behavior of these excitations. Here, we use momentum-resolved electron energy loss spectroscopy (q-EELS) in a transmission electron microscope to explore the optical response of plasmonic thin films including momentum transfer up to wavevectors (q) significantly exceeding the light line wave vector. We show close agreement between experimental q-EELS maps, theoretical simulations of fast electrons passing through thin films and the momentum-resolved photonic density of states (q-PDOS) dispersion. Although a direct link between q-EELS and the q-PDOS exists for an infinite medium, here we show fundamental differences between q-EELS measurements and the q-PDOS that must be taken into consideration for realistic finite structures with no translational invariance along the direction of electron motion. Our work paves the way for using q-EELS as the preeminent tool for mapping the q-PDOS of exotic phenomena with large momenta (high-q) such as hyperbolic polaritons and spatially dispersive plasmons.
Publication date
PublisherAmerican Chemical Society
LanguageEnglish
AffiliationNational Institute for Nanotechnology; National Research Council Canada
Peer reviewedYes
NPARC number23002392
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Record identifier8c70892d-6f90-400f-b93d-4e21b259840c
Record created2017-10-26
Record modified2017-10-26
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