Narrow and Deep Fano Resonances in a Rod and Concentric Square Ring-Disk Nanostructures

Yanyan Huo,Yi Zhang,Hua Zhao,Tianqing Jia,Shian Zhang,Donghai Feng,Zhenrong Sun

doi:10.3390/s130911350

Yanyan Huo, Yi Zhang + Show 5 more

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https://doi.org/10.3390/s130911350

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Journal: Sensors (Basel, Switzerland)	Publication Date: Aug 26, 2013
Citations: 52	License type: CC BY 3.0

Affiliation: East China Normal University

Abstract

Localized surface plasmon resonances (LSPRs) in metallic nanostructures have been studied intensely in the last decade. Fano interference is an important way to decrease the resonance linewidth and enhance the spectral detection resolution, but realizing a Fano lineshape with both a narrow linewidth and high spectral contrast-ratio is still challenging. Here we propose a metallic nanostructure consisting of a concentric square ring-disk (CSRD) nanostructure and an outside nanorod. Fano linewidth and spectral contrast ratio can be actively manipulated by adjusting the gap between the nanorod and CSRD, and by adjusting the gap between the ring and disk in CSRD. When the gap size in CSRD is reduced to 5 nm, the quadrupolar Fano linewidth is of 0.025 eV, with a contrast ratio of 80%, and the figure of merit reaches 15.

Highlights

Fano resonance in metallic nanostructures has gained much attention in recent years
We propose a metallic nanostructure consisting of an outside rod and a concentric square ring-disk (CSRD) nanostructure, which is abbreviated as RCSRD
In order to understand the variation of line width and contrast ratio of the quadrupolar Fano resonances, we investigate the dark quadrupolar mode of the CSRD nanostructure

Summary

Introduction

Fano resonance in metallic nanostructures has gained much attention in recent years. It arises from the constructive and destructive interference of a narrow dark mode and a broad bright mode [1,2,3].Fano resonances were considered mostly in quantum systems [4], but they have been realized in many metallic nanostructures, such as dolmen nanostructures [5,6], nanoparticle clusters [7,8,9,10,11,12], and ring-disk nanocavities [13]. Fano resonance in metallic nanostructures has gained much attention in recent years. It arises from the constructive and destructive interference of a narrow dark mode and a broad bright mode [1,2,3]. Fano resonances were considered mostly in quantum systems [4], but they have been realized in many metallic nanostructures, such as dolmen nanostructures [5,6], nanoparticle clusters [7,8,9,10,11,12], and ring-disk nanocavities [13]. Nanorod structures are easy to fabricate, and Fano resonances are commendably realized in these nanostructures [15,16,17,18,19].

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