Magnetic Nanoparticles Functionalized Few-Mode-Fiber-Based Plasmonic Vector Magnetometer.

Yaofei Chen,Guishi Liu,Jiangli Dong,Yongchun Zhong,Jianhui Yu,Yaxin Zhang,Weiting Sun,Yunhan Luo,Wenguo Zhu,Zhe Chen

doi:10.3390/nano9050785

Abstract

In this work, we demonstrate a highly-sensitive vector magnetometer based on a few-mode-fiber-based surface plasmon resonance (SPR) sensor functionalized by magnetic nanoparticles (MNPs) in liquid. To fabricate the sensor, a few-mode fiber is side-polished and coated with a gold film, forming an SPR sensor that is highly sensitive to the surrounding refractive index. The vector magnetometer operates based on the mechanism whereby the intensity and orientation of an external magnetic field alters the anisotropic aggregation of the MNPs and thus the refractive index around the fiber SPR device. This, in turn, shifts the resonance wavelength of the surface plasmon. Experimental results show the proposed sensor is very sensitive to magnetic-field intensity and orientation (0.692 nm/Oe and −11.917 nm/°, respectively). These remarkable sensitivities to both magnetic-field intensity and orientation mean that the proposed sensor can be used in applications to detect weak magnetic-field vectors.

Highlights

Magnetic sensing is important in the industry, power transmission, military, etc
In this paper, aiming to develop a higher sensitivity magnetometer with the ability of simultaneous sensing to the magnetic intensity and orientation, we propose and investigate a plasmonic vector magnetometer based on a side-polished few-mode-fiber (FMF) functionalized by magnetic nanoparticles (MNPs)
The employing Noafnosmidatee-rpialosl2i0s1h9e, d9, Fx MFOFR, PwEhERicRhEhVaIEsWa non-circularly-symmetric geometry and a relatively-smal1le0rocfo1r3e diameter compared to multimode fibers, makes the proposed senor possess the highest sensitivity to magneticT-fiaebllde-1o.rCieonmtaptairoinso.ns between the smartphone-based and the traditional platforms

Summary

Introduction

Magnetic sensing is important in the industry, power transmission, military, etc. In recent years, optical-fiber magnetic-field sensors, integrated with magnetic nanoparticles (MNPs) in liquid that is called magnetic fluids (MFs) or ferrofluids, have attracted considerable attention because of their ease of fabrication, high sensitivity and low cost [1]. Based on the mechanism whereby protein binding can tailor the response to a magnetic field, these devices have recently been used to measure protein concentrations [19,20], further extending the range of applications to biosensing Most of these sensors were designed to detect the magnetic intensity while ignoring the magnetic orientation, due to the lack of exploration on the microstructure of MF around the optical fiber. Schwendtner et al experimentally boosted the sensitivity up to ~1 nm/Oe by using a tapered fiber as an SPR substrate [31] These SPR-based MF sensors were only proposed to detect magnetic field intensity, but not orientation. Zhang et al demonstrated a plasmonic fiber-optic vector magnetometer based on directional scattering between polarized plasmon waves and ferro-magnetic nanoparticles, and achieved the sensitivities of 0.18 nm/Oe and 2 nm/◦ to intensity and orientation, respectively [21]. The excellent characteristics of this sensor and its operating mechanism are comprehensively analyzed offering an effective solution for high-sensitivity magnetic-vector sensing

Principles and Structure

Response to Magnetic-Field Intensity

Discussion

Conclusions