28 September 2007 Local-field and multipole effects in second-harmonic generation from gold nanoparticles and nanodimers
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Abstract
Nanoscale variations in the local fields and material properties can enable higher-multipole (magnetic-dipole and electric-quadrupole) contributions to the nonlinear response in addition to electric-dipole contributions. Moreover, the local-field distribution in the structure is important to achieve favorable interaction with the locally varying nonlinearity. Local-field enhancement is particularly important for nonlinear optical effects. Extremely small features of a few nm, such as nanogaps between two particles, are expected to be particularly beneficial for field localization and enhancement. Here, we provide evidence of multipole interference in polarized secondharmonic generation from arrays of L-shaped gold nanoparticles. We also prepare T-shaped gold nanodimers and vary the size of the nanogap between their vertical and horizontal bars. Surprisingly, the second-harmonic signals do not decrease trivially with increasing gap size, because the gap region is nearly centrosymmetric, thereby forbidding second-order effects. Instead, asymmetric local fundamental field distributions along the dimer perimeter are favorable, in accordance with the symmetry rule.
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Martti Kauranen, Brian K. Canfield, Sami Kujala, Hannu Husu, Benfeng Bai, Janne Laukkanen, Markku Kuittinen, Yuri Svirko, Jari Turunen, "Local-field and multipole effects in second-harmonic generation from gold nanoparticles and nanodimers", Proc. SPIE 6641, Plasmonics: Metallic Nanostructures and Their Optical Properties V, 66410P (28 September 2007); doi: 10.1117/12.731234; https://doi.org/10.1117/12.731234
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