Article

Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers

Data Storage Institute, (A*STAR) Agency for Science Technology and Research, 5 Engineering Drive 1, 117608 Singapore.
Optics Express (Impact Factor: 3.53). 03/2011; 19(6):4949-56. DOI: 10.1364/OE.19.004949
Source: PubMed

ABSTRACT Arrays of plasmonic pentamers consisting of five metallic nano-disks were designed and fabricated to achieve a pronounced Fano Resonance with polarization-independent far-field spectral response at normal incidence due to the structure symmetry of pentamers. A mass-spring coupled oscillator model was applied to study plasmon interactions among the nano-disks. It was found that the direction of the excitation light polarization can flexibly tune the spatial localization of near-field energy at sub-wavelength scales while the collective optical properties are kept constant. It can lead to a selective storage of excited energy down to sub-20 nm gap at a normal incident with a single light source.

Download full-text

Full-text

Available from: Amir Tavakkoli, Apr 24, 2014
0 Followers
 · 
90 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arrays of planar symmetric gold quadrumers consisting of a central nano-disc surrounded by three similar nano-discs belonging to the D(3h) point group were designed and fabricated. Since the geometrical configuration of quadrumers is the same as planar trigonal molecules, nano-discs can play the roles of artificial atoms to study the coupling trends among them. The plasmonic properties of the nano-disc structures are investigated by reflection spectrum measurement and finite-difference time-domain calculation with good agreement. Plasmon interaction among the nano-discs is also studied via a mass-spring coupled oscillator model. A pronounced Fano resonance (FR) is observed for the fabricated nano-discs with inter-disk gaps of around 18 nm during light irradiation at normal incidence. Although the obtained FR is independent of the excitation polarization, the near-field energy spatial distribution can be flexibly tuned by the polarization direction. This has potential applications in nano-lithography, optical switching and nonlinear spectroscopy.
    Nanotechnology 06/2011; 22(24):245204. DOI:10.1088/0957-4484/22/24/245204 · 3.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We study the plasmonic properties of silver–silica–silver multilayer nanoshells using finite-difference time-domain methods. Silver is a weakly dissipating metal and is able to support higher order resonances compared to strongly dissipating metals like gold. We show that Fano resonances occur even in symmetric cases. Symmetry breaking via the introduction of core offset further enhances these Fano resonance peaks and leads to the appearance of higher order resonances. The optical properties of the multilayer nanoshells are explained using the plasmon hybridization theory and the results are compared to similar multilayer nanoshells with gold core and outer shell.
    Applied Physics A 04/2012; 107(1). DOI:10.1007/s00339-012-6757-1 · 1.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arrays of planar symmetric coupled oligomers support higher sensitivity optical response than uncoupled plasmonic systems. In this work, the transition from isolated to collective optical modes in plasmonic oligomers, such as pentamers and quadrumers, is investigated via experimental characterization and simulation with good agreement. The designed and fabricated metallic oligomers consist of a single central disk and outer ring-like disks in nanoscales. It is shown that while the far-field spectral responses of oligomers are polarization-independent, due to the structure symmetry, the spatial localization of near-field energy in nanogaps can be polarization-controlled. This localization is established at a normal-incident light of a single source rather than co-illumination by two light sources accompanied by different incident angles or phase shift. It can overcome the spatial restrictions of conventional optics. The influence of the nano-disk sizes and gaps among them on the intensity and shape of the localized near-field energy in pentamers and quadrumers is also studied.
    Applied Physics A 04/2011; 107(1). DOI:10.1007/s00339-011-6732-2 · 1.69 Impact Factor