Third harmonic imaging of plasmonic nanoantennas - PowerPoint PPT Presentation

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Third harmonic imaging of plasmonic nanoantennas

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  1. Andreas Trügler, Ulrich Hohenester Karl-Franzens-Universität Graz, Austria Third harmonic imaging of plasmonicnanoantennas Work performedtogetherwith: T. Hanke, J. Cesar, R. Bratschitsch, A. Leitenstorfer Lehrstuhl für Moderne Optik und Quantenelektronik, Univ. Konstanz

  2. Goal of this work Tailoringspatiotemporallightconfinement in singlenanoantennas… 200 nm Agenda • - Optical antennas, experiments • Simulation of metallic nanoparticles • THG mappingofparticleplasmons 200 nm

  3. Nanoantennasasnonlinearemitters Hyper-Rayleigh scattering at surface imperfections, see M. Stockman et al., PRL 92, 057402 (2004) Linear optics: Resolution givenbywavelengthl Nonlinearoptics (THG): Resolution givenbyl / 3 Excitation vs. Detection: Wavelengthdifference Strong χ(3)nonlinearityforgold, see T. Hanke et al., PRL 103, 257404 (2009)

  4. Imaging withoptical antennas Substrate THG intensity ~ | E |6 E THG Pump laser pulse 0.97 eV, 24 fs Array of nanoantennas Byscanningtheexcitationspotoverthe sample andobservingthe THG signal (in thefarfield), weobtain a mapoftheelectricfieldsoftheparticleplasmons. See S. Kim et al., High-harmonic generation by resonant plasmon field enhancement, Nat. Lett. (2008); T. Hanke, R. Bratschitsch, A. Leitenstorfer @ Univ. Konstanz, Germany (2011).

  5. THG mappingofparticleplasmons Third harmonic generation (THG) map (left) and sample (right) Excitation with fs – pulses and with a bandpass filter for wavelengths 1100 – 1500 nm T. Hanke, R. Bratschitsch, A. Leitenstorfer @ Univ. Konstanz, Germany (2011).

  6. THG mappingofparticleplasmons T. Hanke, R. Bratschitsch, A. Leitenstorfer @ Univ. Konstanz, Germany (2011).

  7. THG intensityforparticleplasmons Lowestantennavolume giveshighestTHG intensity !?

  8. Boundaryelementmethod (BEM) Discretizationofsurface integral into „boundaryelements“ Collocationmethod … surfacechargeslocatedatcentersofboundaryelements fromboundaryconditions… F. J. García de Abajo et al., PRB 65, 115418 (2002); U. Hohenester et al., PRB 72, 195429 (2005).

  9. THG mappingofparticleplasmons Simulation ofantennastructures Resultfromexperiment Size ofeachtriangle ca. 300 nm, discretisationwith 20.000 surfaceelements

  10. THG intensityforparticleplasmons Lowestantennavolumegiveshighest THG intensity !? Scatteringintensitygeneratedbyelectromagneticfieldsatthesurface… Incoherentoptics: Biggestvolumegiveshighestintensity… Coherentoptics: Lowestvolumesgiveshighestintensity…

  11. THG autocorrelation Autocorrelation allows to measure dephasing time of particle plasmons THG autocorrelationintensitydepends on time delaybetweenfemtosecondpulses

  12. THG autocorrelation Autocorrelationallowstomeasuredephasing time ofparticleplasmons harmonicfields Insert harmonicfieldstogetherwithplasmondamping time: damping twointeractingpulses in / out ofphaseratiogives 32:1 THG autocorrelationintensitydepends on time delaybetweenfemtosecondpulses

  13. THG autocorrelation Autocorrelation allows to measure dephasing time of particle plasmons Dephasingtimes: rod 5.5 fs ellipse 3.5 fs disc 2.0 fs THG autocorrelationintensitydepends on time delaybetweenfemtosecondpulses Weak plasmon damping effective build-up of the plasmonoscillation Knowledge of the plasmon damping time alone suffices to predict the nonlinear intensity !

  14. THG intensity vs. plasmondephasing THG intensitydirectlyscaleswithplasmondephasing ! Long dephasingtimescorrespondto large THG intensities 30 47 64 81 98 115 132 149 166 183 200 high nonlinear emission connected to small antenna volumes radiative damping! rodlength: 300 nm gap: 50 nm

  15. THG intensity vs. plasmondephasing THG intensitydirectlyscaleswithplasmondephasing ! Long dephasingtimescorrespondto large THG intensities

  16. Summary & Acknowledgement TheoreticalNanoscience Ulrich Hohenester Jürgen Waxenegger KFU Graz, Austria Temporal scale: Measuring few-fs plasmon damping times Spatial scale: Mapping of third-harmonic emission Radiative damping: Lowest volumes generates strongest third-harmonic emission Moderne Optik und Quantenelektronik Alfred Leitenstorfer Rudolf Bratschitsch Tobias Hanke Vanessa Knittel Julijan Cesar High intensity linked to smallest antenna volume!