Induced electric fields and plasmonic interactions between a metallic nanotube and a thin metallic film

Abstract

We have numerically simulated the induced electric fields and the plasmonic interactions of a metallic nanotube near a thin metallic film. Our study shows that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube as well as the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. The enhancement of the induced electric field of this system reaches as high as 10 4 orders of magnitude and its field distribution is characterized by waveguide-mode resonance. The report proposes that these phenomena can be applied to designing surface enhanced spectroscopies such as surface enhanced Raman spectroscopy for efficient chemical and biological sensing. metallic nanotube, virtual state, plasmons, extinction spectrumSurface plasmons (SPs) are coupled oscillations of electrons and electromagnetic fields which propagate along the metallic surfaces. This phenomenon has generated an enormous interest in the optical research community [1-4]. Since appropriate techniques are available for fabricating metallic nanostructures, much progress has been made not only in understanding the optical properties of metallic nanosystems but also in their applications. The unique optical phenomena such as optical waves guiding beyond the diffraction limit in plasmonic waveguides [1], surfaceenhanced Raman scattering in optical antennas for ultrasensitive chemical and biomolecular detections [3], and fluorescence through plasmonic resonant light scattering [5], have been exploited for various applications.The plasmonic properties are highly dependent on the size, the shape of the nanostructure and the surrounding dielectric environment for a single nanostructure [6,7]. However, when different types of metallic nanostructures form a nanosystem, such as nanoparticle with nanowire [8], metal nanoparticle array [9, 10], and metal ring/disk nanocavities [11], the plasmon modes can be modified by additional plasmonic resonances, energy shifts and energy confinements created by the interactions of the individual nanostructures. Therefore, the plasmonic properties of these nanosystems have attracted a considerable amount of research efforts.The plasmons of a finite nanostructure can be considered discrete eigenmodes characterized by the spatial symmetry of their associated surface charge distribution [12]. Problems involving the discrete plasmons of a finite nanostructure such as a nanoshell [13] or a nanosphere [14], interacting with a continuum of delocalized plasmons have been studied. The interaction results in localized states, resonances, and virtual states (VSs) in the continuum. These concepts were originally introduced to describe the nature of the electronic states resulting from the interaction of a discrete impurity level with a continuum, and have also been used to describe the interaction of localized and delocalized photonic states in photonic crystals.In our recent paper [15], v...

Plasmons in Strongly Coupled Metallic Nanostructures

“…Metallic nanoparticle interactions with a nearby substrate or surface represents a class of systems of fundamental importance and of great utility in applications. ,− The presence of any substrate, dielectric, semiconducting, or metallic, breaks the symmetry of the nanoparticle environment and has a strong influence on the modes of the nanoparticle. Here we consider the basic physics of the nanoparticle–substrate interaction in several contexts, the role of plasmon interactions, and the properties of several coupled nanoparticle–substrate systems.…”

Tunable plasmon resonances in a metallic nanotip–film system

“…The plasmonic interaction between metallic nanoparticles and adjacent metallic films has been studied extensively, [9][10][11][23][24][25][26][27][28][29] and is here discussed only briefly. The interaction depends on the relative size of the nanoparticle and the thickness of the film.…”