Article

# Multipole interference in the second-harmonic optical radiation from gold nanoparticles.

Optics Laboratory, Institute of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland.

Physical Review Letters (Impact Factor: 7.73). 05/2007; 98(16):167403. DOI: 10.1103/PhysRevLett.98.167403 Source: PubMed

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**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.ACS Photonics. 05/2014; 1(6):471–476. - [Show abstract] [Hide abstract]

**ABSTRACT:**The discrete rotational symmetry of nanostructures provides a powerful and simple guiding principle for designing the second-harmonic generation process in nonlinear metamaterials. We demonstrate that, in achiral nanostructures with threefold rotational symmetries, a circularly polarized fundamental beam produces a countercircularly polarized second-harmonic beam. In this case, the polarization state of the second harmonic is determined in a very simple manner. We also demonstrate how rotational symmetries in nonlinear metamaterials manifest themselves in SHG selection rules.Physical Review Letters 04/2014; 112(13):135502. · 7.73 Impact Factor -
##### Article: Second-harmonic response of multilayer nanocomposites of silver-decorated nanoparticles and silica.

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**ABSTRACT:**We perform a detailed characterisation of the second-order nonlinear optical response of nanocomposites consisting of alternating layers of silver-decorated silica glass nanoparticles and pure silica glass. The samples are fabricated using aerosol techniques and electron-beam dielectric coating, resulting in a bulk-like material with symmetry-breaking induced by the porosity of the alternating layers. The second-order nonlinear response increases with the number of layers. Further, by determining the components of the second-order susceptibility tensor of the samples, we show that the structural properties of the samples are well maintained as the sample thickness is increased. Our results form an important baseline for any further optimization of these types of structures, which can be fabricated using very straightforward methods.Scientific Reports 07/2014; 4:5745. · 5.08 Impact Factor

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