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.