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Dipole-Quadrupole Coupling in Rod-Sphere Metallic Nanodimer for Second-Harmonic Generation

Research output: Other conference contributionPaper, poster or abstractProfessional


Original languageEnglish
Number of pages1
Publication statusUnpublished - 2017
Duration: 1 Jan 1900 → …


Period1/01/00 → …


The optical properties of noble metals arise from the plasmonic oscillations of conduction electrons. The plasmon resonances can give rise to strong local fields (“hotspots”) near metal surfaces. For nanoparticles (NPs), localized surface plasmons (LSP) exhibit a high degree of optical field confinement. LSP resonances of individual NPs are sensitive to their size and shape, type of metal, and dielectric environment. However, the quality of the LSP resonances (line width and field enhancement) depends on the lifetime of the localized plasmonic excitations. The longer is the plasmon lifetime, the narrower the linewidth and the stronger the field enhancement will be.
A pioneering pathway to improve the optical response of plasmonic systems is to use plasmonic Fano resonances (PFR). The PFR, which is the result of the interference between bright (superradiant) and dark (subradiant) modes in metallic nanostructures, gives rise to reduced radiative loss resulting in strong near-field enhancement and a tunable resonance. Here, a simple structure composed of exquisiotely-controlled assembly of a nanodimer consisting of a metal nanosphere and nanorod is designed to generate PFR in the near infrared region.
We investigated and analyzed the dependence of the PFR in such a structure on its geometrical parameters such as the size of the rod and the sphere, their interparticle separation. We also addressed different excitation polarization, including linear, azimuthal, and radial polarizations. We show that PFR is polarization-dependent and exhibits high sensitivity to the geometrical parameters. In order to verify that this structure can generate a second-harmonic generation (SHG) response, we calculated the extinction cross-section and the near-field distributions at the fundamental and SHG wavelengths. In addition to that, the preliminary experimental results agree with the numerical study, indicating that an excitation at the PRF resonance leads to an enhancement of the SHG response of the rod-sphere metallic nanodimer.

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