This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiber-optic analogues of the Kretschmann–Raether prism SPR platforms, made from geometry-modified multimode and single-mode optical fibers (unclad, side-polished, tapered, and U-shaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively.

/pdf/review-of-plasmonic-fiber-optic-biochemical-sensors-rt43n8tfhr.pdf

Review of plasmonic fiber optic biochemical sensors: improving the limit of detection.

The development of highly-sensitive miniaturized sensors that allow real-time quantification of analytes is highly desirable in medical diagnostics, veterinary testing, food safety, and environmental monitoring. Photonic Crystal Fiber Surface Plasmon Resonance (PCF SPR) has emerged as a highly-sensitive portable sensing technology for testing chemical and biological analytes. PCF SPR sensing combines the advantages of PCF technology and plasmonics to accurately control the evanescent field and light propagation properties in single or multimode configurations. This review discusses fundamentals and fabrication of fiber optic technologies incorporating plasmonic coatings to rationally design, optimize and construct PCF SPR sensors as compared to conventional SPR sensing. PCF SPR sensors with selective metal coatings of fibers, silver nanowires, slotted patterns, and D-shaped structures for internal and external microfluidic flows are reviewed. This review also includes potential applications of PCF SPR sensors, identifies perceived limitations, challenges to scaling up, and provides future directions for their commercial realization.

/pdf/photonic-crystal-fiber-based-plasmonic-sensors-wyb2yrls3t.pdf

Photonic crystal fiber based plasmonic sensors

We propose a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) with selectively filled analyte channels. Silver is used as the plasmonic material to accurately detect the analytes and is coated with a thin graphene layer to prevent oxidation. The liquid-filled cores are placed near to the metallic channel for easy excitation of free electrons to produce surface plasmon waves (SPWs). Surface plasmons along the metal surface are excited with a leaky Gaussian-like core guided mode. Numerical investigations of the fiber’s properties and sensing performance are performed using the finite element method (FEM). The proposed sensor shows maximum amplitude sensitivity of 418 Refractive Index Units (RIU−1) with resolution as high as 2.4 × 10−5 RIU. Using the wavelength interrogation method, a maximum refractive index (RI) sensitivity of 3000 nm/RIU in the sensing range of 1.46–1.49 is achieved. The proposed sensor is suitable for detecting various high RI chemicals, biochemical and organic chemical analytes. Additionally, the effects of fiber structural parameters on the properties of plasmonic excitation are investigated and optimized for sensing performance as well as reducing the sensor’s footprint.

/pdf/photonic-crystal-fiber-based-surface-plasmon-resonance-1ywwhi6pmy.pdf

Photonic Crystal Fiber-Based Surface Plasmon Resonance Sensor with Selective Analyte Channels and Graphene-Silver Deposited Core

A surface plasmon resonance (SPR) sensor with two open-ring channels based on a photonic crystal fiber (PCF) is described. The sensor is designed to detect low refractive indexes between 1.23 and 1.29 with the operation wavelength in mid-infrared region between 2550 nm and 2900 nm. The coupling characteristics and sensing properties are numerically analyzed by the finite element method. The average spectral sensitivity is 5500 nm/RIU and a maximum resolution of 7.69 × 10-6 RIU can be obtained. Our analysis shows that the PCF-SPR sensor is suitable for mid-infrared detection.

Mid-infrared surface plasmon resonance sensor based on photonic crystal fibers

A simple multi-core flat fiber (MCFF) based surface plasmon resonance (SPR) sensor operating in telecommunication wavelengths is proposed for refractive index sensing. Chemically stable gold (Au) and titanium dioxide (TiO2) layers are used outside the fiber structure to realize a simple detection mechanism. The modeled sensor shows average wavelength interrogation sensitivity of 9,600 nm/RIU (Refractive Index Unit) and maximum sensitivity of 23,000 nm/RIU in the sensing range of 1.46-1.485 and 1.47-1.475, respectively. Moreover, the refractive index resolution of 4.35 × 10−6 is demonstrated. Additionally, proposed sensor had shown the maximum amplitude interrogation sensitivity of 820 RIU−1, with the sensor resolution of 1.22 × 10−5 RIU. To the best of our knowledge, the proposed sensor achieved the highest wavelength interrogation sensitivity among the reported fiber based SPR sensors. Finally we anticipate that, this novel and highly sensitive MCFF SPR sensor will find the potential applications in real time remote sensing and monitoring, ultimately enabling inexpensive and accurate chemical and biochemical analytes detection.

Highly sensitive multi-core flat fiber surface plasmon resonance refractive index sensor.

Multi-hole fiber based surface plasmon resonance sensor operated at near-infrared wavelengths

The invention provides a two-dimensional integrated optical fiber online storage based on a linear array multi-core optical fiber. The two-dimensional integrated optical fiber online storage is formed by connecting a single-mode optical fiber (7) with one section of array multi-core side-throwing optical fiber (2); and metal gradient grating structures (4) are formed on the surfaces of a plurality of naked fiber cores (3) by utilizing an optical micro-processing technology. The principle applied by the invention is based on a rainbow local effect, namely, a chromatic dispersion effect of the gradient grating is used for resonantly limiting plasmons with different wavelengths into different space positions; and light with different wavelengths can be stopped into two-dimensional space positions with different optical fiber side-throwing planes, so that the online two-dimensional storage of optical signals from visible light to optical signals of infrared bands can be realized. The device has the advantages of small volume, simple structure and high integration degree, can easily realize full-optical-fiber integration and has an important application on the optical fiber online storage field.

Two-dimensional integrated optical fiber online storage based on linear array multi-core optical fiber

A novel surface plasmon resonance (SPR) sensor based on the multihole optical fiber with TiO 2 layer is proposed and numerically characterized. The finite element method(FEM) is used to analyze the characteristics of the SPR sensor. The effects of the pitch between air holes, the thicknesses of the gold film and titanium dioxide layer on the sensor characteristics are investigated, and the sensitivity of proposed sensor is also given. The results indicate that when the thickness of gold film increases, the resonance wavelength shif ts to longer wavelength, and the resonance peak broadens. The spectral tuning of the plasmon resonance can be more efficiently realized by changing the TiO 2 layer thickness. The maximal refractive-index resolution of the proposed sensor for aqueous analytes is 5×10 -5 . 1. INTRODUCTION Optical fiber surface plasmon resonance (S PR) sensors are the unique combination of optical fiber technology and SPR technology. In the past few decades, the optical fiber SPR sensor has been widely applied in biochemical detection, environmental and food testing, structural health monitoring

Yaowu Wen

Papers

Multi-hole fiber based surface plasmon resonance sensor operated at near-infrared wavelengths

Two-dimensional integrated optical fiber online storage based on linear array multi-core optical fiber

Surface plasmon resonance sensor based on multihole optical fiber with TiO2 layer