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Ultrafast nanoscience @ELI-ALPS

Ultrafast nanoscience @ELI-ALPS. Péter DOMBI h ead of Scientific Applications D ivision. e lectric field nanolocalization with plasmons. Important properties : Nanoscale localization of electric field of light Field enhancement … … but how much exactly ?. 100 nm.

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Ultrafast nanoscience @ELI-ALPS

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  1. Ultrafastnanoscience @ELI-ALPS Péter DOMBI head of ScientificApplicationsDivision

  2. electricfieldnanolocalizationwithplasmons Importantproperties: Nanoscalelocalization of electricfieldoflight Fieldenhancement … … buthowmuchexactly? 100 nm

  3. plasmonfieldcontrolwithnanoparticlegeometry EM fieldnanolocalization Fieldenhancement: asmuchas x1000 (!)

  4. importance of nanooptical/plasmonic near-fields • applicationsin: • surfaceenhancedRamanscattering • photovoltaics • plasmonic sensors • cancertherapy, nanosurgery • nanostructuredphotocathodes • etc.

  5. motivation: ultrafastplasmonicdevices • builidingultrafastnanoopticaldevicesforsignalprocessing, switching etc. • few-cyclelaserpulsesarehighly important e.g. in attophysics // Can we makefew-cycleplasmonwavepackets?

  6. Fieldenhancement and dynamicsprobingof nanoopticalswitchingarchitecture mod in 0 1 0 1 1 1 out 0 1 0 ~20 nm (nottoscale)

  7. electricfieldnanolocalizationwithplasmons important properties: nanoscalelocalization of electricfield fieldenhancement … … buthowmuchexactly?

  8. a challenge • can we measuretheabsolute plasmonic fieldenhancementvalueforanymetallicsurfacesample • with an ultrafasttool • in a direct, robust, non-destructivemanner? • (differentthanmapping)

  9. an earlierexperiment Time-of-flightelectronspectrometer Dombi et al., Nano Lett. 13, 674 (2013) Ultrafastphotoemissionintoplasmonicfield 80-fs laserpulses 5 kHz repetitionrate

  10. plasmonresonancestronglyinfluenceselectronspectra Dombi et al., Nano Lett. 13, 674 (2013) laserspectrum

  11. thequestion • canweusetheseelectronspectratoextractabsolutefieldenhancementvalues?

  12. 1. Near-fieldprobingwithultrafastelectrons2. Time-resolvedprobing

  13. approachformeasuringfieldenhancement fsnear-fieldstimulatesphotoemission spectra of photoelectronscan be measured photoelectronsrescatteredatthesurfacehavethehighestkineticenergy 4. Qmax = 10,007 e2λ2Eloc2/ (16 2mc2) 5. rescatteringtakesplaceinnanometricvolumes Nearfield maximum can be measuredwithphotoelectrons

  14. electronoscillationamplitude <0.7 nm beforerescattering Qmax = 10,007 e2λ2Eloc2/ (16 2mc2) alsofornanotips: Thomas et al., Nano Lett. 2013

  15. measuringfieldenhancementon test nanosurfaces Qmax = 10,007 e2λ2Eloc2/ (16 2mc2) Rácz et al., Nano Lett. 17, 1181 (2017)

  16. Validation Rácz et al., Nano Lett. 17, 1181 (2017)

  17. Validation ← experiment vs. simulation 36.1 vs. 31.7 51.2 vs.50.5 Rácz et al., Nano Lett. 17, 1181 (2017)

  18. FDTD validation Edge/cornerradii accordingto SEM images No fittingparameters! Rácz et al., Nano Lett. 17, 1181 (2017)

  19. whatcanweusethistoolfor? – plasmon-plasmoncoupling …and thus plasmon-plasmon coupling electronsprobingfieldenhancement… localized plasmon propagatingplasmon light

  20. Couplingbetweenpropagating and localizedmodes J. Budai et al., Nanoscale10, 16261 (2018)

  21. Fieldenhancement (FE) contributions fromlocalized and propagatingplasmons Smooth, experimental FE = 20 Rougher, experimental FE = 22 Roughest, experimental FE = 31 Localizedplasmon Propagatingplasmon J. Budai et al., Nanoscale10, 16261 (2018)

  22. Resonance of localizedplasmoncontribution

  23. Dipolecontributiontonear-field Field of a dipole Field 20 nm abovesurfacegrain J. Budai et al., Nanoscale10, 16261 (2018)

  24. 1.Near-fieldprobingwithultrafastelectrons2. Time-resolvedprobing

  25. Time-resolved probing of few-cyle plasmon transients broadextinction narrowextinction pol.

  26. Experimentalscheme 5.5 fs 80 MHz Photoemissionnonlinearity: Workfunction: ~5 eV Photon energy: 1.3-2 eV Effectivenonlinearity: ~3.3

  27. Time-resolvedprobing of few-cyle plasmon transients broadextinction narrowextinction pol.

  28. Reconstruction of plasmontransient reconstructed measured 8-fs plasmon transient

  29. Condensedmatteruserendstation

  30. The condensed phase/surface science end station Nanoesca system of Scienta Omicron Core capability: photoemission electron microscopy (PEEM) The sample, illuminated by ultrashort NIR and/or XUV pulses is the electron source for the electron microscope optics. • imaging with a broadrange of field of views (2.5 mm-1 mm) • resolution down to 50 nm or better • realtime imaging of the surface. • Lensesproject a magnified image of the sample to a 2D detector.

  31. Energy resolved PEEM Nanoesca system of Scienta Omicron • Small Spot Spectroscopy mode • High sensitivity single-spot spectroscopy using the channeltron for quantitative elemental analysis. A quickspectrumfromtheactualfield of view. Energyresolvedimaging(Imaging ESCA mode). The main lens projects the magnified image onto the analyzerentrance. The image information is energy filtered (energyresolution: 50 meV) by highly aberration correcting IDEA & projected onto a MCP/screen stack for camera based date acquisition.

  32. Local angleresolvedphotoemission (ARPES) The electron optics can be set to image the momentum space: electrons originated from different sample points but departing at the same angle will reach the detected at the same point. Real space k-space kx , ky ,E resolved and imaged IDEA: Imaging Energy Filter Band structure of graphene Electrons are collected from ~2p solid angle without any rotation of the sample

  33. Summary • sub-nm sensitivityhot spot probingwithphotoelectrons • generation of few-cycleplasmontransientswithoff-resonantexcitation • ultrafastdeviceoperation in complexplasmonicarchitectures • few-fselectronsourcesforelectronmicroscopy • ELI-ALPS toolsenhancing • ultrafastplasmonicsresearch

  34. Time scales in solids Energy bandwidth / eV 1 0.1 0.01 0.001 Screening Dephasing e-e scattering e-phonon scattering 0.1 1 10 100 1000 Time scale / fs Adapted from Petek, Ogawa, Progr. Surf Sci. 1997 Easily achievable laser pulse duration Optical period at 800nm Electron emission duration

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