Angular Scattered Light Intensity of Dipole–Multipole Plasmonic Hybridization

Abstract

The coupled plasmonic modes of noble metal nanoparticles are of interest in fields spanning chemistry, physics, materials science, and biology. We systematically investigated the near- and far-field optical response of a dipole–multipole (D–M) coupled gold nanorod (Au NR) dimer structure. We show that the coupling behavior of D–M resonances leads to redshifted bonding and blueshifted antibonding modes that are analogous to the dipole–dipole coupling observed in the plasmon hybridization framework of Nordlander et al. In particular, the antibonding modes of Au NR dimers are very similar to multipolar resonances of the Au NR monomer of equivalent overall length. These antibonding modes show almost identical far-field plasmon resonance peaks and near-field distribution and also have similar far-field angular radiation profiles with even stronger intensities. We also evaluated Au NR dimer structures of different gap distances in terms of near-field intensities, phase changes, and angular scattering patterns, which exhibit coupling behavior ranging from strongly interacting D–M systems to uncoupled individual elements over a variety of gap distances. Our studies may advance the fundamental understanding of D–M coupled plasmonic systems and pave the path to new opportunities for nanoplasmonic applications, such as fluorescence imaging, energy storage, biosensors, metamaterials, etc.

Parallel Aligned Dipole–Multipole Plasmonic Hybridization

“…The simulated spectra of the gap ( g = 5 nm) separated dimers with X , Y , and Z direction-aligned L short – L long combinations are summarized in Figure h,i. Particularly, the case of alignment in the Y direction showed different coupled modes compared to the other two cases, which has been discussed in our previous work where the antibonding mode of M 1 – M ′ l Au NR dimer behaves as 2 l +1 -pole in terms of far-field resonance, near-field distribution, and angular radiation patterns …”

“…Particularly, the case of alignment in the Y direction showed different coupled modes compared to the other two cases, which has been discussed in our previous work where the antibonding mode of M 1 −M′ l Au NR dimer behaves as 2 l+1 -pole in terms of far-field resonance, near-field distribution, and angular radiation patterns. 33 On the other hand, the Au NR dimer structure aligned in X and Z directions showed similar far-field extinction spectra. It is noteworthy that after being developed into the coupled dimer structure, the long NR's multipolar resonance was split into two modes.…”

“…The background electric field wavelength was set relative to the applied vacuum medium, and the model was solved for the scattered field. Similar to our previous work, calculations were performed for orthogonal (α = 90°) and oblique (α = 45°) illuminations to excite the odd mode and even mode of Au NR monomer, respectively. , Specifically, for the Au NR dimer structure, we set orthogonal (α = 90°) illumination for M l =1 – M ′ l =2 and oblique (α = 45°) illumination for M l =1 – M ′ l =3 .…”

“…The coupling mode in the “plasmonic molecule” structure has been investigated to explore how the plasmon resonances of individual “plasmonic atoms” interact with those in adjacent nanostructures. − Particularly, the head-to-head-assembled one-dimensional nanorod dimer structure has been studied extensively. − Previous studies have shown that the higher-order mode of Au NR monomer is similar to the antibonding mode of the Au NR dimer structure of equivalent overall length in terms of both near- and far-field optical properties. , …”

“…25−32 Previous studies have shown that the higherorder mode of Au NR monomer is similar to the antibonding mode of the Au NR dimer structure of equivalent overall length in terms of both near-and far-field optical properties. 9,33 Despite end-to-end assembly, other-shape arranged plasmonic molecules have been reported. For example, Yun et al proposed a very simple nanorod dimer with a T-shaped arrangement to produce strong Fano resonances.…”