Role of electric currents in the Fano resonances of connected plasmonic structures

Abstract

In this work, we use finite elements simulations to study the far field properties of two plasmonic structures, namely a dipole antenna and a cylinder dimer, connected to a pair of nanorods. We show that electrical, rather than near field, coupling between the modes of these structures results in a characteristic Fano lineshape in the far field spectra. This insight provides a way of tailoring the far field properties of such systems to fit specific applications, especially maintaining the optical properties of plasmonic antennas once they are connected to nanoelectrodes. This work extends the previous understanding of Fano resonances as generated by a simple near field coupling and provides a route to an efficient design of functional plasmonic electrodes.

Electromagnetic Forces and Torques: From Dielectrophoresis to Optical Tweezers

“…90 As a result, higher multipolar orders have been more extensively studied at optical frequencies and have found a wider range of applications, for example, in explaining the nonlinear response of optical systems 91 and the spectral features of Fano resonant structures. 92,93 The interference and coupling between different orders has also been used to explain the directional scattering properties of particles and the resulting optical force. 32,37,94−99 Again, we point out that the eq 17 and eq 5, used to calculate the higher order multipoles, are correct only for electrostatic fields.…”

“…However, at higher frequencies the typical field wavelength becomes comparable or smaller than the particle size, and the higher multipolar contributions come into play . As a result, higher multipolar orders have been more extensively studied at optical frequencies and have found a wider range of applications, for example, in explaining the nonlinear response of optical systems and the spectral features of Fano resonant structures. , The interference and coupling between different orders has also been used to explain the directional scattering properties of particles and the resulting optical force. ,,− Again, we point out that the eq and eq , used to calculate the higher order multipoles, are correct only for electrostatic fields. While they can still be safely adopted when the low-frequency fields used in DEP are employed, they do not anymore provide a correct description of the force at higher field frequencies.…”

Strong and weak polarization-dependent interactions in connected and disconnected plasmonic nanostructures

“…1,2 Following theoretical predictions, 3 Fano resonance has been observed in various types of structures such as inter alia: nanoclusters, 4 plasmonic particles involving nanorods, metalinsulator-metal systems, 5,6 and between interconnected metal structures. 7 A fundamental condition for the observation of a Fano prole is the interference between spectrally-overlapping broad and discrete modes. 8 As so-called dark-modes display weak scattering losses, they generally play the role of narrow resonance, while the broad one results from the excitation of a bright mode with a strong dipolar component.…”