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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: 7.51). 05/2007; 98(16):167403. DOI: 10.1103/PhysRevLett.98.167403
Source: PubMed

ABSTRACT We provide experimental evidence of higher multipole (magnetic dipole and electric quadrupole) radiation in second-harmonic (SH) generation from arrays of metal nanoparticles. Fundamental differences in the radiative properties of electric dipoles and higher multipoles yield opposite interference effects observed in the SH intensities measured in the reflected and transmitted directions. These interference effects clearly depend on the polarization of the fundamental field, directly indicating the importance of multipole effects in the nonlinear response. We estimate that higher multipoles contribute up to 20% of the total emitted SH field amplitude for certain polarization configurations.

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    • "Once the nonlinear sources have been established, they radiate SHG light according to the emission rules of the electric and magnetic dipole sources [29] [30]. For coherent signals emitted along the sample normal to the reflected and transmitted directions, the SHG signals in the far field are proportional to "
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    ABSTRACT: We present a detailed multipolar tensor analysis of second-harmonic (SH) generation from arrays of L-shaped gold nanoparticles. We define three effective nonlinear tensors, which include electric dipoles only (Aeee) and lowest-order magnetic (and quadrupole) effects at the fundamental (Aeem) and the SH (Amee) frequency. The components of the various tensors are distinguished through their different transformations as the experimental geometry is varied. The response is dominated by electric-dipole effects. However, the higher multipoles also play a significant role and are more important at the fundamental frequency than at the SH frequency. The results correlate well with the particles' plasmonic resonances and symmetry rules.
    New Journal of Physics 02/2011; 13(2):023025. DOI:10.1088/1367-2630/13/2/023025 · 3.67 Impact Factor
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    • "When the nanoscale features become sufficiently large, however, we must also consider field retardation across such features. The retardation effects can lead to an effective quadrupolar response, as observed in incoherent hyper-Rayleigh scattering from individual nanoparticles [34] [35] and in coherent SHG from lithographically designed nanostructures [19] [20]. "
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    ABSTRACT: New Journal of Physics Vol.12 Nr.6, 063009 Gold films of 20 and 150 nm nominal thickness were characterized by two-beam second-harmonic generation to address their second-order nonlinear optical responses of surface (dipolar) and bulk (higher multipolar) origin. The surface response is enhanced by ~20% in the case of the 20 nm film, as expected due to its higher surface roughness. Surprisingly, the bulk-type response is enhanced to a greater extent, exceeding 80%, and this can be explained by effective quadrupolar nonlinearity arising from the field interaction with the local nonlinearity of nanoscale surface features. Gold films of 20 and 150 nm nominal thickness were characterized by two-beam second-harmonic generation to address their second-order nonlinear optical responses of surface (dipolar) and bulk (higher multipolar) origin. The surface response is enhanced by ~20% in the case of the 20 nm film, as expected due to its higher surface roughness. Surprisingly, the bulk-type response is enhanced to a greater extent, exceeding 80%, and this can be explained by effective quadrupolar nonlinearity arising from the field interaction with the local nonlinearity of nanoscale surface features.
    New Journal of Physics 03/2010; 12:063009. DOI:10.1088/1367-2630/12/6/063009 · 3.67 Impact Factor
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    • "As a consequence, in some cases the nonlinear signals were dominated by tensor components not allowed for the ideal structure [23]. We have also shown that the defects can give rise to SHG emission with higher multipole characteristics, i.e., radiation that appears to originate from effective magnetic dipoles or electric quadrupoles [26] [27]. Extremely small nanoscale features, such as sharp tips or nanogaps between two particles, are expected to give rise to very strong local fields. "
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    ABSTRACT: We review the state-of-the-art regarding the second-order nonlinear optical response of metal nanostructures and metamaterials. The present nanofab- rication of metal nanostructures gives rise to defects and other deviations from the ideal structure. Such factors may break the intended symmetry of the structure and give rise to nonlinear signals, which are ideally forbidden. Although second-order effects are electric-dipole-forbidden in the bulk of centrosymmetric materials, they become allowed through magnetic- dipole and electric-quadrupole effects. Improved understanding of the role of the surface and bulk effects in the second-order response of metals is needed in order to develop proper theoretical models for nonlinear metal nanostructures.
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