Analysis of Scattering by Plasmonic Gratings of Circular Nanorods Using Lattice Sums Technique.

Jandieri Jandieri,Yasumoto Yasumoto,Pistora Pistora,Erni Erni

doi:10.3390/s19183923

Jandieri Jandieri, Yasumoto Yasumoto + Show 2 more

Open Access

https://doi.org/10.3390/s19183923

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Abstract

A self-contained formulation for analyzing electromagnetic scattering by a significant class of planar gratings composed of plasmonic nanorods, which were infinite length along their axes, is presented. The procedure for the lattice sums technique was implemented in a cylindrical harmonic expansion method based on the generalized reflection matrix approach for full-wave scattering analysis of plasmonic gratings. The method provided a high computational efficiency and can be considered as one of the best-suited numerical tools for the optimization of plasmonic sensors and plasmonic guiding devices both having a planar geometry. Although the proposed formalism can be applied to analyze a wide class of plasmonic gratings, three configurations were studied in the manuscript. Firstly, a multilayered grating of silver nanocylinders formed analogously to photonic crystals was considered. In the region far from the resonances of a single plasmonic nanocylinder, the structure showed similar properties compared to conventional photonic crystals. When one or a few nanorods were periodically removed from the original crystal, thus forming a crystal with defects, a new band was formed in the spectral responses because of the resonant tunneling through the defect layers. The rigorous formulation of plasmonic gratings with defects was proposed for the first time. Finally, a plasmonic planar grating of metal-coated dielectric nanorods coupled to the dielectric slab was investigated from the viewpoint of design of a refractive index sensor. Dual-absorption bands attributable to the excitation of the localized surface plasmons were studied, and the near field distributions were given in both absorption bands associated with the resonances on the upper and inner surfaces of a single metal-coated nanocylinder. Resonance in the second absorption band was sensitive to the refractive index of the background medium and could be useful for the design of refractive index sensors. Also analyzed was a phase-matching condition between the evanescent space-harmonics of the plasmonic grating and the guided modes inside the slab, leading to a strong coupling.

Highlights

With the rapid development of nanoscience and nanotechnology, the interaction of light with nanoscaled objects remains as an important issue in photonics because of their novel applications to sensors, imaging, and densely integrated devices [1,2,3,4,5,6,7]
Scattering of an incident plane wave by plasmonic gratings composed of a periodic arrangement of metal and metal-coated dielectric nanocylinders was rigorously investigated utilizing our original formalism based on the lattice sums technique [10,11,12]
A rigorous self-consistent formulation was efficiently applied to a wide class of plasmonic gratings composed of metal and metal-coated nanocylinders

Summary

Introduction

With the rapid development of nanoscience and nanotechnology, the interaction of light with nanoscaled objects remains as an important issue in photonics because of their novel applications to sensors, imaging, and densely integrated devices [1,2,3,4,5,6,7]. The goal of the manuscript is to apply the proposed formalism to various configurations of plasmonic structures and demonstrate its usefulness from the viewpoint of flexible design, of plasmonic sensors, and filters, reflectors, and guiding plasmonic devices. An understanding of the frequency bands, in which the electromagnetic wave propagation is suppressed, is an important issue in flexibly designing plasmonic guiding devices with relative low losses. The defects were introduced by periodically removing one or a few nanocylinders from a PhC layer This approach gives us additional freedom to flexibly design the reflection and transmission bands as desired under the prescribed structural parameters, which is not possible for conventional configurations (structures without defects). The structure was considered from the viewpoint of design of refractive index plasmonic sensors

Formulation of the Problem

Numerical Results and Discussions

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Concluding Remarks