Complex-k modes of plasmonic chain waveguides

Abstract

Nanoparticle chain waveguide based on negative-epsilon material is investigated through a generic 3D finite-element Bloch-mode solver which derives complex propagation constant (k). Our study starts from waveguides made of non-dispersive material, which not only singles out 'waveguide dispersion' but also motivates search of new materials to achieve guidance at unconventional wavelengths. Performances of gold or silver chain waveguides are then evaluated; a concise comparison of these two types of chain waveguides has been previously missing. Beyond these singly-plasmonic chain waveguides, we examine a hetero-plasmonic chain system with interlacing gold and silver particles, inspired by a recent proposal; the claimed enhanced energy transfer between gold particles appears to be a one-sided view of its hybridized waveguiding behavior-energy transfer between silver particles worsens. Enabled by the versatile numerical method, we also discuss effects of inter-particle spacing, background medium, and presence of a substrate. Our extensive analyses show that the general route for reducing propagation loss of e.g. a gold chain waveguide is to lower chain-mode frequency with a proper geometry (e.g. smaller particle spacing) and background material setting (e.g. high-permittivity background or even foreign nanoparticles). In addition, the possibility of building mid-infrared chain waveguides using doped silicon is commented based on numerical simulation.

Plasmonic Properties of Colloidal Assemblies

“…These first-order chain modes (or antisymmetric/dark mode) are also suitable for efficient energy transport along the geometric axes. [73,74] In Figure 2c, the impact of the nature of the metal is illustrated by comparing gold trimers with silver trimers as well as mixed cases. The dashed line indicates that the plasmonic modes are maintained for the selected material combinations.…”

Exploiting Combinatorics to Investigate Plasmonic Properties in Heterogeneous AgAu Nanosphere Chain Assemblies

“…[5a] So far, however, complex assembly techniques like DNA origami, [5a,7] polymeric linkage, [5b] or sequential capillarityassisted particle assembly [8] only allow access to a limited set of such assemblies, making statistically relevant investigations tedious. Thus, long heterogeneous NP chains have been theorized [9] but not synthesized to date.…”

Plasmonic-Induced Transparencies in an Integrated Metaphotonic System

“…Another possibility to induce plasmonic transparencies is by fully embedding nanoparticles (NPs) in the core of the waveguide and taking advantage of the symmetry of the guided modes to excite LSP resonances. These confined architectures reduce scattering losses and increase the contrast of dips in the transmission lines [ 41 , 42 , 43 , 44 ]. However, they have not been exploited for the generation of plasmonic transparency windows.…”