title: Third Harmonic Mechanism in Complex Plasmonic Fano Structures.
abstract: We perform third harmonic spectroscopy of dolmen-type nanostructures, which exhibit plasmonic Fano resonances in the near-infrared. Strong third harmonic emission is predominantly radiated close to the low energy peak of the Fano resonance. Furthermore, we find that the third harmonic polarization of the subradiant mode interferes destructively and diminishes the nonlinear signal in the far-field. By comparing the experimental third harmonic spectra with finite element simulations and an anharmonic oscillator model, we find strong indications that the source of the third harmonic is the optical nonlinearity of the bare gold enhanced by the resonant plasmonic polarization.
authors.affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart , Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Metzger
authors.affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart , Pfaffenwaldring 57, 70569 Stuttgart, Germany ; Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany ; Experimental Physics III, University of Bayreuth , Universitaetsstr. 30, 95447 Bayreuth, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schumacher
authors.affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart , Pfaffenwaldring 57, 70569 Stuttgart, Germany ; Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Hentschel
authors.affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart , Pfaffenwaldring 57, 70569 Stuttgart, Germany ; Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany ; Experimental Physics III, University of Bayreuth , Universitaetsstr. 30, 95447 Bayreuth, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Lippitz
authors.affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart , Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Giessen
keywords: Fano resonance; nano optics; nonlinear optics; plasmonics; spectroscopy; third harmonic generation