GeO2 Doped Optical Fiber Plasmonic Sensor for Refractive Index Detection

Rahul Kumar Gangwar,Rui Min,Santosh Kumar,Xiaoli Li

doi:10.3389/fphy.2021.707113

Rahul Kumar Gangwar, Rui Min + Show 2 more

Open Access

https://doi.org/10.3389/fphy.2021.707113

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Abstract

In this article, a D-shaped optical fiber refractive index (RI) sensor based on surface plasmon resonance effect is demonstrated. The gold film is placed at the flat portion of the optical fiber along with the sensing analytes of the different RIs to excite the plasmonic interactions. Sensing properties are investigated by using the finite element method. The maximum sensitivity of the proposed sensor is achieved as high as 20863.20 nm/RIU with the maximum resolution of 4.79 × 10−6 RIU and figure of merit of 308.38 RIU−1 for an analyte with RI 1.43 by optimizing the different parameters of the sensor with maximum phase matching between the core mode and surface plasmon mode. The high sensitivity of the sensor offers a promising approach for the detection of unknown RI analyte in chemical and biological fields in the near-infrared region.

Highlights

While considerable progress has been made over the last decade in the field of surface plasmon resonance (SPR)–based optical fiber refractive index (RI) sensors, the steady increase in the application of these sensors in several fields such as biological, chemical, and health monitoring etc., always sets a new limit for the research communities [1,2,3]
In SPR phenomena, the evanescent field of TM mode (p-polarized) wave excites the free electrons on the metal surface which produces the surface plasmon (SP) wave propagating through the metal-dielectric interface
It is considered that light propagates in the z-axis and all the model investigation is executed in the XY plane

Summary

Introduction

While considerable progress has been made over the last decade in the field of surface plasmon resonance (SPR)–based optical fiber refractive index (RI) sensors, the steady increase in the application of these sensors in several fields such as biological, chemical, and health monitoring etc., always sets a new limit for the research communities [1,2,3]. In traditional SPR configuration, a total internal reflection–based theory is proposed by Kretschmann and Otto in 1968, in which the base of a coupling prism is coated with the thin metal (Au or Ag) and the incident p-polarized light wave excites the surface plasmons at the metal-dielectric interface [9, 10] This configuration has many limitations and disadvantages like bulk in size, poor reliability, not suitable for remote sensing, and requires mechanical instruments which limit its uses. To overcome these issues, SPR-based micro and nanostructured optical fiber sensors (OFSs) have drawn great attention because of their unique characteristics such as robustness, compact size, fast response, high sensitivity, online real-time monitoring, electromagnetic immunity etc. The first SPR-based OFS, in which a thin gold film is coated on the fiber core for the excitation of the surface plasmon, was proposed by Jorgenson in 1993, and till different kinds of fiber such as tapered fiber [16], multicore fiber [17], fiber grating [18], and photonic crystal fiber (PCF) have been

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