Efficient Coupling to Plasmonic Multipole Resonances by Using a Multipolar Incident Field

Abstract

A method to manipulate the multipolar plasmonic response of a nanostructure in the quasi-static limit is introduced. The theoretical method puts on the same footing geometry, dielectric properties, and incident field and proceeds in two steps: it optimizes the geometry of the nanostructure to maximize the intensity of the scattering crosssection spectrum. This is done by calculating the coupling strengths of the different modes of the system to the external field, which the method naturally provides. Then, it exploits the symmetry of the incident electromagnetic field to enhance or suppress specific orders, which, in turn, tunes the field enhancement. We demonstrate the method by using a plasmonic dimer of nanospheres.

Optical band engineering via vertical stacking of honeycomb plasmonic lattices

“…For l max = 1 we recover the dipole approximation, which is expected to be good for large particle separations [25,35]. For l max = 2 the quadrupole approximation is obtained in which dipole-dipole, dipole-quadrupole and quadrupole-quadrupole moments interactions are taken into account [29].…”

“…3(b)-(c). Since not all modes have a projection onto the dipolar IP or OP base and will therefore have a polarization equal to zero on this basis, in other words, some bands do not couple directly to the dipolar part of the external field but instead require a quadrupolar external field to be directly excited [29]. We can see that bands are neither fully IP or OP, rather than in general, a band has IP and OP regions.…”

“…To describe the response of the system to external excitations, we use the MSR [27,28], which allows a systematic analysis of the system eigenmodes and its dependence on multipolar interactions [29]. This method relies on the multipolar expansion of the electrostatic potential to obtain a set of equations for the induced multipolar charge distribution on each of the particles in the system.…”

“…We begin by applying our method to the case of a honeycomb monolayer of Ag nanospheres with radius a = 10 nm, described by a Drude dielectric function, and hosted within a homogeneous medium of dielectric constant √ h = 1.46, which describe the substrate used in experimental systems [14]. The separation distance between particle centers in a layer is d = 3a, so that we can safely restrict our calculations to the dipole approximation (l max = 1) [29]. This system has been extensively studied due to its analogy with 2-D electronic systems [26].…”

Ultrasonic Influence on Plasmonic Effects Exhibited by Photoactive Bimetallic Au-Pt Nanoparticles Suspended in Ethanol

“…As well, Au NPs have been studied by using acousto-plasmonic interactions [26]. However, the optical and catalytic properties can be improved by combining two different metals at nanometric scale [61], in which, metal composition and shape provide unique functionality [62]. Among the different bimetallic NPs, Au-Pt NPs show higher electrocatalytic activity that represents widely promising functions in catalysis applications, such as a suitable catalyst for methanol oxidation and oxygen reduction reaction [63].…”