Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 13: Plasmonics and nanooptics: Light-matter interaction, spectroscopy I
O 13.4: Talk
Monday, March 12, 2018, 15:45–16:00, MA 041
Wavelength-dependent Third Harmonic Generation in Plasmonic Gold Nanoantennas: Role of the d-band — •Joachim Krauth, Mario Hentschel, and Harald Giessen — 4th Physics Institute and Research Center SCoPE, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
Plasmonic gold nanoantennas are highly efficient nanoscale nonlinear light converters. The nanoantennas provide large resonant light interaction cross sections as well as strongly enhanced local fields. The frequency conversion, however, takes places inside the gold volume and is thus ultimately determined by the microscopic gold nonlinearity. While the influence of the nanoantenna geometry has been studied in great detail, only little attention has been paid to the microscopic material nonlinearity. Here we show that the microscopic third-order nonlinearity of gold is in fact a resonant one by virtue of interband transitions between the d- and sp-bands. Utilizing a large set of resonant nanoantennas and an optical parametric oscillator as broadband tunable light source, we show that the radiated third harmonic (TH) signals significantly increase as soon as the TH becomes resonant with allowed interband transitions. With the help of an anharmonic oscillator model and independent reference measurements on a gold film we can unambiguously demonstrate that the observed TH increase is related to a strongly wavelength-dependent microscopic third-order gold nonlinearity. This additional tuning parameter allows further manipulation and optimization of nonlinear nanoscale systems and thus renders the investigation of other plasmonic materials highly intriguing.