We report the observation of magnetic dipolar contributions to the nonlinear optical (NLO) response of plasmonic nanostructures. Solid gold nanosphere (SGN) dimers and bowties were prepared using colloidal and lithographic methods, respectively. Second-order NLO responses from these particles were examined using polarization-resolved second harmonic generation (SHG) spectroscopy at the single-particle level. Unambiguous circular dichroism in the SHG signal was observed for many of the structures, indicating the presence of a chiral plasmon field within the interparticle gap. Detailed analysis of the polarization line shapes of the SHG intensities obtained by continuous polarization variation suggested that the effect resulted from strong magnetic dipolar contributions to the nanostructure's optical properties. The relative magnetic-dipolar and electric-dipolar contributions to the NLO response were structure dependent, an effect that would have been obscured for ensemble measurements. These findings may be significant for applications using the plasmonic nanostructure platform including nanoantennas, metamaterials, biosensing and energy conversion.

Magnetic dipolar interactions in gold nanoparticle dimers studied by single-particle nonlinear optical spectroscopy

244th National Meeting (2012)

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