title: Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles.
abstract: In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations.
authors: Univ Lyon, UJM-Saint-Etienne, CNRS, Institut d Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, SAINT-ETIENNE, France.
authors: Saïd
authors: S
authors: Bakhti
authors: Univ Lyon, UJM-Saint-Etienne, CNRS, Institut d Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, SAINT-ETIENNE, France.
authors: Alexandre V
authors: AV
authors: Tishchenko
authors: Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France.
authors: Xavier
authors: X
authors: Zambrana-Puyalto
authors: Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France.
authors: Nicolas
authors: N
authors: Bonod
authors: Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors: Scott D
authors: SD
authors: Dhuey
authors: Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors: P James
authors: PJ
authors: Schuck
authors: Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors: Stefano
authors: S
authors: Cabrini
authors: Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors: Selim
authors: S
authors: Alayoglu
authors: Univ Lyon, UJM-Saint-Etienne, CNRS, Institut d Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, SAINT-ETIENNE, France.
authors: Nathalie
authors: N
authors: Destouches