High-order magnetic modes and multiple Fano resonances generation by a Fish-like dimer nanostructure
Abstract
Various noble metal nanostructures based on surface plasmon have been proposed in recent years. Under the irradiation of incident light, if the oscillation frequency of the electrons on the metal surface matches the frequency of the incident light wave, resonance will occur. In the resonance state, a special electromagnetic mode is formed: the electromagnetic field is localized and enhanced in a small area of the structure surface. In our artic, a fish-like dimer (F-LD) nanostructure has been proposed. The dark second order magnetic mode is excited due to the near-field coupling between two parts of the dimer. An asymmetry Fano linetype will be generated when the dark magnetic mode is coupled with the bright electric mode. Rotating the structure, the fourth and sixth order magnetic modes can be generated. When the radii of the semi-rings in the gap are changed, the first and third order magnetic modes can be observed. More interestingly, as the number of semi-ring in the gap increasing, the spectral line shape can be controlled and higher-order magnetic modes can be generated regularly. At the same time, multiple Fano resonances can be observed in the extinction spectrum and the spectrum can be modulated simultaneously in multiple bands. By changing the structure parameters, the first, second, third, fourth, sixth and eighth order magnetic modes can be obtained. In different cases, the magnetic field can be enhanced greatly in different areas of the gap, and the maximum magnetic field enhancement reaches 49 times of the incident field. For these characteristics, our structure can be well used in multi-band sensing and surface enhanced spectroscopy.
- Publication:
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Physica Scripta
- Pub Date:
- May 2020
- DOI:
- 10.1088/1402-4896/ab7850
- Bibcode:
- 2020PhyS...95e5507J
- Keywords:
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- high-order magnetic modes;
- multiple fano resonances;
- plasmonics