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Research Of Surface Plasmon Resonance Refractive Sensor Based On Side-Polished Fiber

Posted on:2017-08-23Degree:DoctorType:Dissertation
Country:ChinaCandidate:J ZhaoFull Text:PDF
GTID:1318330503481769Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Surface Plasmon resonance(SPR) is an emerging technology based on multi-disciplines such as physics, chemistry, biology, biomedical and environmental engineering. Since it was proposed as a potential detection method decades ago, SPR sensing technology has experienced a robust development in chemical analysis, food safety, environmental monitoring as well as in biomedical and other sciences. SPR can be excited at the interface between the thin metallic film and the dielectric media,and the propagation constant strongly depends on the refractive index(RI) of the surrounding medium. Therefore, even very small changes in the RI adjacent to metal layer can produce a measurable shift in the resonant dip. With the tendency to miniaturization and networking of sensor, the optical-fiber-based SPR allows for a smaller sample volume, real-time and label-free detection, and become the most promising research in the RI detection area.Specifically, a side-polished fiber(SPF) with the fiber cladding removed to access the evanescent field of the guide mode was designed to be coupled with the SPR technology due to, among others, low manufacturing cost, the flat polished surface good for depositing uniform metal film, and the strong evanescent field to excite SPR. Typically, the SPR sensors deposited with metals such as gold or silver have good RI response and high sensitivities. Silver-coated sensor enables sharpest resonant dip, higher resolution and lower cost than gold-coated sensor. However,degradation of the silver in ambient air and moisture environment can change the metal composition and decrease the interfacial adhesion force of silver film. One of the goals of the thesis was to evaluate how silver degradation influences the sensing performance of SPR device, and how to protect the silver film as well as enhance the self-assembly ability to biomolecule in the following bio-chemical sensing application base on the side-polished fiber SPR sensor. Here, several part of research point exist in this thesis as:Firstly, this thesis demonstrated a mechanical wheel lapping technique to fabricate a convenient and low cost side-polished fiber by use of the abrasive papers with different roughness. Through the fabrication process as coarse grinding, fine grinding, fine polishing and arc-discharge polishing, the SPF were optimized to obtain a high surface quality as well as controlled optical performance, which is the basis for the further development of SPF-based SPR sensor. As an innovation, the SPF fabricated only by the coarse grinding process has a rough, rather than smooth,polished surface. Such a bare coare-SPF can be directly used to develop a promising sensing device, because Mach-Zehnder interference(MZI) pattern with high fringe contrast above 10 dB in transmission spectrum was achieved due to the optimized macro scratches on the rough polished surface. The coarse-sensor exhibited fast response to axial-strain, temperature, refractive index as well as the concentration of alcohol gas, and can be used as a low-cost disposal evanescent fiber sensor.Secondly, this thesis demonstrated a surface plasmon resonance refractive sensor based on the side-polished single mode optical fiber and investigated the sensor performance decay induced by silver coating degradation. As a substitution for the micro-fluidic cell, a simple refractive index test platform is proposed. The sensor showed fast response to the refractive index liquid in the range from 1.32 to 1.40 RIU,with a highest sensitivity up to 4365.5 nm/RIU and a figure of merit(FOM) of 51.61RIU-1. Characteristics of the silver-coated sensor exposed to the air as well as to the liquid environment were compared, and providing a basis for the usage and storage of the silver-based SPR sensor. The presented silver-coated sensor could be used as a simple, cost-effective, disposable device in bio-chemical, environment, and food safety detection.Thirdly, the proposed silver-SPR sensor based on side-polished fiber was futher modified by the single or few-layer of graphene oxide(GO) through the Self-Assembly(SAM) method, to give a protection for the silver-SPR sensor as well as a high assembility layer for biomolecule absoption in future bio-chemical detection.In this part of research, the stripped GO sol-solution was prepated and verified by Tyndall effect as well as UV-absorptiong spectrum. The process of SAM was in-linemonitored to make sure ODT/GO film was attached onto the sensing area. Beside a higher stability, the comparision experiment shows that the silver-SPR sensor modified by single or few-layer of GO filme present an enhanced RI response sensitivity, and can be used as a fiber bio-chemical SPR sensor with high assembility for biomolecule in future sensing application.
Keywords/Search Tags:Optical fiber sensor, Surface Plasmon Resonance, Side-polished fiber, Refractive sensor, Graphene Oxide
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