Plasmonic Nanodimers Research Articles

Multipole polarizability of a nanodimer in optical waves

In this work we study the interaction of visible light with plasmonic nanodimers that, under particular illumination conditions, do not exhibit any electric dipole excitations. It has previously been found out that the dipole suppression phenomenon disappears when the illumination direction is reversed. As a consequence, a homogeneous nanomaterial consisting of such nanodimers can be expected to be spatially dispersive, such that the conventional electric polarization vanishes for certain directions of light propagation. In order to reveal the complete picture of the light-nanodimer interaction, we analyze the multipole excitations in a dimer at various illumination angles. In particular, we introduce an analytical model for the multipole polarizability tensors of the dimer that, in contrast to conventional polarizability tensors, depend on the light propagation direction. The model is verified by rigorous numerical calculations. It can be used to gain insight into the properties of optical nanomaterials, such as metamaterials, in which higher-order multipoles can be efficiently excited.

Palladium bridged gold nanocylinder dimer: plasmonic properties and hydrogen sensitivity

Plasmonic nanodimers facilitate electromagnetic hotspots at their gap junction. By loading these gap junctions with nanomaterials, the plasmonic properties of nanodimer can be varied. In this study, we bridged the gap junction of gold (Au) nanocylinder dimer with palladium (Pd), and numerically evaluated the plasmonic properties of the designed nanostructure. We simulated the far-field extinction spectra of Pd bridged Au nanocylinder dimer, and identified the dipole and quadrupole plasmon modes at 839 and 578 nm, respectively. By varying the geometrical parameters of the Pd bridge, we revealed the ability to tune the dipolar plasmon resonance of the bridged dimer. Further, we exploited the hydrogen sensitivity of Pd bridge to harness the bridged-Au dimer as nanoplasmonic hydrogen sensor. Such nano-optical detection platforms have minimal spatial footprint and can be further harnessed for chip-based plasmonic sensing.

Hertzian plasmonic nanodimer as an efficient optical nanoantenna

Inspired by the geometry and shape of the classical radio-frequency radiator, the Hertzian dipole, here we analyze the design of a plasmonic optical dimer nanoantenna. We show how it may be possible to operate a pair of closely spaced spherical nanoparticles as an efficient optical nanoradiator, and how its tuning and matching properties may be tailored with great degree of freedom by designing suitable nanoloads placed at the dimer gap. In this sense, we successfully apply nanocircuit concepts to model the loading nanoparticles. High levels of optical radiation efficiency are achieved, even considering the realistic absorption of optical metals, thanks to this specific geometry and design.