Refractive Index Nanosensor With Simple Structure Based on Fano Resonance

Jing Guo,Mengmeng Wang,Xiaoyu Yang,Ertian Hua,Yifei Wang,Shubin Yan

doi:10.1109/jphot.2020.3015988

Abstract

Herein, a refractive-index sensor is theoretically proposed, which comprises metal-insulator-metal waveguide and single rectangle cavity without a long side (RCWALS). The propagation characteristics were analyzed by finite element method. Compared with the contrastive structure, the designed single RCWALS structure has better transmission spectra and stronger resonance and supports Fano resonance. The effects of the structural parameters on sensing characteristics were investigated. Mode 1 of single RCWALS structure has better performance parameter, which is the best sensitivity of 1840 nm/RIU with a figure of merit of 51.11. Additionally, three derived structures are presented, which are composed of MIM waveguide and two RCWALS in different positions. They have lower sensitivity but better figure of merit, and provide more detection positions. The designed structures, which are greatly simple, can potentially apply to nanophotonics.

Highlights

The single RCWALS structure is composed of a MIM waveguide and single rectangle cavity without a long side (RCWALS)
Narrow full width at half maximum (FWHM) is the reason for small optical resolution and better figure of merit (FOM)
The propagation characteristics were investigated by the finite element method (FEM)

Summary

Introduction

Surface plasmon polaritons (SPPs) are charge-density waves, which are largely trapped on metaldielectric interface and can transmit along the interface [1], [2]. SPPs-based nanosensor is an important application, which has advantages of smaller size as well as being easy to integrate into optical circuits and get in touch with sensing mediums. Different geometry structures or mediums environments could largely lead to the change of dip or peak position of Fano resonance. The combination of Fano resonance and MIM coupled system could accomplish great sensitivity with a small size. Yan et al [25] designed a nanosensor with sensitivity of 1071.4 nm/RIU, which comprises one stub and one notched ring resonator. Zhang et al [27] proposed coupled structure of double rectangle cavities and MIM waveguide, whose sensitivity is 596 nm/RIU. The simple-structure refractive-index nanosensor comprises a MIM waveguide and single rectangle cavity without a long side (RCWALS). Three derived structures are presented, and their sensing characteristics were investigated

Geometry Model and Analysis Method

Simulations and Results

Derived Structures and Their Propagation Properties

Conclusion