Refractive Index Sensor Based on Fano Resonances in Metal-Insulator-Metal Waveguides Coupled with Resonators.

Yue Tang,Ruibing Wang,Wendong Zhang,Zhidong Zhang,Zhenyin Hai,Shubin Yan,Chenyang Xue

doi:10.3390/s17040784

Yue Tang, Ruibing Wang + Show 5 more

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https://doi.org/10.3390/s17040784

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Abstract

A surface plasmon polariton refractive index sensor based on Fano resonances in metal–insulator–metal (MIM) waveguides coupled with rectangular and ring resonators is proposed and numerically investigated using a finite element method. Fano resonances are observed in the transmission spectra, which result from the coupling between the narrow-band spectral response in the ring resonator and the broadband spectral response in the rectangular resonator. Results are analyzed using coupled-mode theory based on transmission line theory. The coupled mode theory is employed to explain the Fano resonance effect, and the analytical result is in good agreement with the simulation result. The results show that with an increase in the refractive index of the fill dielectric material in the slot of the system, the Fano resonance peak exhibits a remarkable red shift, and the highest value of sensitivity (S) is 1125 nm/RIU, RIU means refractive index unit. Furthermore, the coupled MIM waveguide structure can be integrated with other photonic devices at the chip scale. The results can provide a guide for future applications of this structure.

Highlights

Surface plasmon polaritons (SPPs) are the charge-density waves caused by coupling between photons and electrons on the metal surface [1,2]
MIM of waveguides are simulated under varying resonator and between the lower and upper parts of the ring resonator
A plasmonic refractive index sensor based on MIM waveguides coupled with rectangular and ring resonators is studied by finite-element method (FEM)

Summary

Introduction

Surface plasmon polaritons (SPPs) are the charge-density waves caused by coupling between photons and electrons on the metal surface [1,2]. Their fields decay exponentially in the direction perpendicular to the metal–dielectric interface [3,4,5,6,7,8]. SPPs overcome the diffraction limit of light waves [9,10], rendering them suitable for nanoscale photonic devices [11,12,13,14,15]. Many photonic devices based on Fano resonances have been designed

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