Sensitivity Enhancement of a Concave Shaped Optical Fiber Refractive Index Sensor Covered with Multiple Au Nanowires.

Pathak Pathak,Rahman Rahman,Kumari Kumari,Singh Singh

doi:10.3390/s19194210

Abstract

In the present paper, a new kind of concave shaped refractive index sensor (CSRIS) exploiting localized surface plasmon resonance (LSPR) is proposed and numerically optimized. The LSPR effect between polaritons and the core guided mode of designed CSRIS is used to enhance the sensing performance. The sensor is characterized for two types of sensing structures coated with gold (Au) film and Au nanowires (AuNWs), respectively. The influence of structural parameters such as the distance (D) of the concave shaped channel (CSC) from the core, the diameter of the nanowire (dn) and the size (s) of the CSC are investigated here. In comparison to Au film, the AuNWs are shown to significantly enhance the sensitivity and the performance of the designed sensor. An enhanced sensitivity of 4471 nm/RIU (refractive index unit) is obtained with AuNWs, for a wide range of analytes refractive index (na) varying between 1.33 to 1.38. However, for conventional Au film; the sensitivity of 808.57 nm/RIU is obtained for the same range of analytes.

Highlights

Surface plasmon resonance (SPR) is the resonant oscillation of the conduction electrons at the metal–dielectric interface, which is stimulated by the incident light [1]
The proposed concave shaped refractive index sensor (CSRIS) is based on the localized surface plasmon resonance (LSPR) phenomenon that takes place between the surface plasmon polaritons (SPP) and the core guided modes
We have designed a new kind of CSRIS for a wide range of refractive index (RI) sensing in this paper

Summary

Introduction

Surface plasmon resonance (SPR) is the resonant oscillation of the conduction electrons at the metal–dielectric interface, which is stimulated by the incident light [1]. The matching of wave vector of incident wave with the surface plasmon (SP) leads to the popularly known phenomenon of SPR at the metal–dielectric interface [2,3], while the LSPR phenomenon refers to the collective oscillations of the electron charge confined around the metallic nanostructures and demonstrate enhanced near-field amplitude at the resonance wavelength [4]. In the traditional SPR configuration reported by Kretschmann, a prism with a thin metal deposited on its base was used, and the SPs were excited on the metal–dielectric interface in the presence of p polarized light, at a certain angle. The prism based free space SPR configuration is bulky in size and may not be suitable for remote sensing, which limits its application and large-scale fabrication for real monitoring

Methods

Results

Conclusion