Collective electric and magnetic plasmonic resonances in spherical nanoclusters

Abstract

We report an investigation on the optical properties of three-dimensional nanoclusters (NCs) made by spherical constellations of metallic nanospheres arranged around a central dielectric sphere, which can be realized and assembled by current state-of-the-art nanochemistry techniques. This type of NCs supports collective plasmon modes among which the most relevant are those associated with the induced electric and magnetic resonances. Combining a single dipole approximation for each nanoparticle and the multipole spherical-wave expansion of the scattered field, we achieve an effective characterization of the optical response of individual NCs in terms of their scattering, absorption, and extinction efficiencies. By this approximate model we analyze a few sample NCs identifying the electric and magnetic resonance frequencies and their dependence on the size and number of the constituent nanoparticles. Furthermore, we discuss the effective electric and magnetic polarizabilities of the NCs, and their isotropic properties. A homogenization method based on an extension of the Maxwell Garnett model to account for interaction effects due to higher order multipoles in dense packed arrays is applied to a distribution of NCs showing the possibility of obtaining metamaterials with very large, small, and negative values of permittivity and permeability, and even negative index.

Complex modes and artificial magnetism in three-dimensional periodic arrays of titanium dioxide microspheres at millimeter waves

“…Similar results may be achieved by using arrays made of nanoshell particles [25,[29][30]. Also, the packing of plasmonic nanoparticles in an engineered fashion to create nanoclusters [31][32][33] allows for the generation of artificial magnetism.…”

“…Accordingly, the SDA is a good approximation when particle dimensions are much smaller than the wavelength, and when the edge-to-edge spacing d between spheres is larger than the spheres' radius r (i.e., d ≥ r). However, even for smaller distances, the SDA may provide satisfactory approximated results [33], though in general, for a spacing between the spheres smaller than their radius (i.e., 0 < d < r), more accurate results may involve multipole field contributions [44,[46][47][48].…”

Effect of irregularities of nanosatellites position and size on collective electric and magnetic plasmonic resonances in spherical nanoclusters

“…Clusters of self-assembled plasmonic nanoparticles can be used as building blocks for new magnetic or negative index materials at optical frequencies [1][2][3][4][5][6][7]. In particular, nanoclusters (NCs) of spherical shape formed by a number of satellites made of silver nanocolloids, each enclosed within a thin dielectric shell, and all attached to a dielectric core of variable size can provide isotropic electric and magnetic resonances in three-dimensions (3D) [6].…”

Giant Magnetic Field Enhancement in Hybridized MIM Structures

“…As a result, the magnetic plasmon resonance appears in the optical-NIR range of the spectrum [2,3]. Several structures have been proposed in the literature to demonstrate magnetic hot spots including nanorings [4], MIM nanosandwiches [5][6][7] and nanoparticle clusters [8,9]. The MIM structure (nanosandwich) consists of two metallic strips separated by a dielectric layer.…”