MtPh

Watching plasmons spin on atomically flat single crystalline gold

Datum
06.12.2018 
Zeit
11:00 Uhr - 12:00 Uhr 
Sprecher
Prof. Dr. Harald Giessen 
Institut
4th Physics Institute, University of Stuttgart, Stuttgart, Germany 
Teil der Serie
IFW Kolloquium 
Sprache
en 
Hauptthema
Materialien: Supraleiter, Magnetwerkstoffe, Nanostrukturen
Subthemen
Physik: Condensierte Materie (incl. Soft, Festkörper)
Ansprechpartner
 
Zusammenfassung

We use single crystalline gold flakes on atomically flat silicon substrates to generate ideally suitable interfaces for plasmon propagation. By electrochemical means, the thickness is tunable from a few tens to over 100 nm. Using sub-20 fs laser pulses around 800 nm, we excite surface plasmons, whose dynamics can be observed using time-resolved two-photon excitation electron emission (PEEM).

Plotting the dispersion of surface plasmons in a thin gold slab on silicon, one finds that excitation at 800 nm can lead to extreme wavelength reduction due to the dispersion slop of over five. Using focused ion beam for cutting rings with appropriate periodicity into the samples (see left image), we can excite concentric surface plasmons that create a nanofocus of only 60 nm width for 800 nm excitation (see center image) [1].

Figure 1. Atomically flat single crystalline gold with PEEM images of short-range surface plasmons. Nanofocusing down to 60 nm at 800 nm wavelength is observed, as well as orbital angular momentum plasmons up to l=4.

Archimedean spirals with broken n-fold radial symmetry excite surface plasmons with angular orbital momentum on the gold flakes (see right image). This leads in case of 4-fold symmetry to cloverleaf-type nanofoci on the order of 100 nm, which rotate during four optical cycles by 360 degrees [2].

Two-pulse experiments with a subwavelength-stabilized Michelson interferometer, allow investigation of the surface pattern dynamics with (sub-) femtosecond resolution, thus giving insight into the dynamics of the nanofocus formation as well as on the plasmonic spin-orbit coupling [3].

 

Letzte Aktualisierung: 06.12.2018 00:05.

Vortragsort 

Leibniz Institut für Festkörper- und Werkstoffforschung Dresden (A1E.10, Hörsaal, IFW Dresden) 
Helmholtzstraße 20
01069 Dresden
Homepage
http://www.ifw-dresden.de 

Veranstalter 

Leibniz Institut für Festkörper- und Werkstoffforschung Dresden (IFW)
Helmholtzstraße 20
01069 Dresden
Homepage
http://www.ifw-dresden.de 
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