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Interslit Coupling via Ultrafast Dynamics across Gold-Film Hole Arrays
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posted on 2014-05-22, 00:00 authored by Roman Walther, Itai Carmeli, Reinhard Schneider, Dagmar Gerthsen, Kurt Busch, Christian Matyssek, Ayala Shvarzman, Tsofar Maniv, Shachar Richter, Hagai CohenOne-dimensional
arrays of submicrometer rectangular holes in 200 nm thin gold films
are investigated using electron energy loss spectroscopy combined
with scanning transmission electron microscopy (STEM-EELS). Improved
energy resolution, down to 0.11 eV, is accomplished in our monochromated
transmission electron microscope, allowing the reliable quantification
of signals at loss energies as small as 0.43 eV. The standing-wave
resonances of individual holes are thus investigated at nanometer-scale
spatial resolution, focusing in particular on the effect of neighboring
holes. We show how the coupling between holes is facilitated by surface
plasmon polaritons (SPPs) propagating on the top and bottom surfaces
of the separating metal-film strips. Thus, complex spatiotemporal
coupling dynamics emerges, characterized by strong interslit interactions
and a phase that can be controlled by varying the width of the metal
strip between adjacent holes. Applying real-space real-time numerical
simulations and exploiting the short interaction time of 300 keV electrons
with the thin gold film, we reveal intriguing features of these ultrafast
coupling mechanisms, including unusual line-narrowing and marked SPP
signal enhancements in the corresponding EEL spectra. Complementary
aspects of the far-field and near-field components in the SPP eigenstates
are further demonstrated. Our combined analysis effectively equips
STEM-EELS with an excellent temporal resolution and further yields
a consistent description of the entangled femtosecond-scale SPP dynamics.
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gold filmsdynamicComplementary aspects0.11 eVSPP signal enhancementsmetal stripEEL spectrabottom surfacesmonochromated transmission electron microscope300 keV electrons0.43 eVenergy resolutioninterslit interactionsloss energiesSPP eigenstatesUltrafast Dynamicsinteraction timesurface plasmon polaritons200 nmelectron energy loss spectroscopyscanning transmission electron microscopygold film
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