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Title: Designing and modelling of surface plasmon sensors using photonic quasi crystal fibres
Author: Chu, Suoda
ISNI:       0000 0004 9358 5385
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2020
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The sensing applications based on surface plasmon resonance (SPR) have been developed rapidly in recent decades. Much attention has been paid for its real time sensing and label-free detection ability. A commercial success of the application on SPR technique is the BiacoreTM SPR systems developed by General Electric (GE) Heathcare. It has been widely used in hospitals and research institutes in various fields from biomedical/chemical reaction detection to the environment monitoring and food safety controlling. However, this prism-based SPR sensing system suffers from its bulk size design, moderate sensitivity and high cost. Further, the invention of optical fibre accelerated the development of SPR sensors, named as fibre optical plasmon sensor (FOPS) by utilizing the conventional optical fibre. It has been proven to be a potentially promising tool for the realisation of small-size sensor with excellent sensing performance and the capability of remote sensing. The FOPS has a significant importance on the development of SPR sensors in various ways. Later on, the emergence of photonic crystal fibre (PCF)with FOPS has opened up a new era of sensing technological innovations. The PCF based FOPS is now becoming a promising optical detection technique for studying label-free bio-molecular interactions in real time. In this thesis, the use of novel PCFs as a new class of optical fibre together with the SPR phenomenon for sensing application is presented and investigated in detail. By manipulating the structural parameters, the PCFSPR sensor can be optimized to achieve higher sensitivity, larger sensing range for better sensing performance and easy-fabrication. Additionally, efforts have been made to investigate the influence of the sub-peak for higher order SPR on the sensing performance. Moreover, a multi-sensing scheme by utilizing metallic nanowires in PCF may provide a new method for fast sensing. The key original contributions of this thesis include: 1. Modified D-shaped PQF-SPR Bio-sensor with Trapezoid Shaped Analyte Channel for High Refractive Index Liquid Analytes with Adjustable Liquid Height. To overcome those two disadvantages - low sensitivity and fabrication difficulty and to extend the sensing range, a six-fold trapezoidal channel (TC) PQF SPR bio-sensor for liquid bio-analyte sensing is demonstrated to investigate how the liquid height in the TC influences the sensing performance. The structure optimization of such sensor is presented for better sensitivity, sensing range and stability. The effective refractive indices and loss spectra peak differences acquired from the simulations of the designed TC-PQF sensor for a range of wavelengths have been solved and calculated thoroughly to evaluate its sensing performance. According to the numerical results, it shows a good sensitivity for the analyte RI ranges of 1.40 to 1.58 which is broad enough to cover most of the bio-samples. Besides, the result also proves that it is possible to control the sensor's detection range by adjusting the liquid analyte's height/thickness. The liquid analyte height/thickness is also found to influence the sensor's sensing performance and an inversely proportional relationship between the detection sensitivity and detectable analyte RI range has been concluded. This work helps us to gain an understanding on the effect of the quantity/height of the analyte of interest and the structural parameters on the sensing performance of such kind of PQF-SPR bio-sensor. Part of the work in the previous project is to form a side-channel into the fibre structure so that the liquid height can be varied in such channel. Although a detailed fabrication method of the proposed sensor with trapezoidal side-channel has been clearly discussed in chapter 3, a mature fabrication/manufacture process for this unique structure is not available on the market for massive production. Hence, from a commercial perspective, it would be economical and realizable to apply a common type of PCF, which is already available on the market as the substrate for sensors fabrication. Therefore, the six-fold hexagonal D-shaped PCF is introduced in the sensor design for easy-fabrication purpose. 2. The Influence of Secondary Plasmon Resonance Peak on the Sensing Performance of a Standard Six-fold D-shaped PCF-SPR Sensor. The side-polish technique currently is used to produce D-shaped PCF which has been widely studied by many researchers as a relatively mature post-processing method in lab. For this reason, it is necessary to introduce and investigate the sensing performance of such a six-fold D-shaped hexagonal PCF-SPR sensor. Its sensing details have been discussed and concluded in chapter 4 about the influence of different plasmonic resonance peaks between the fundamental mode and surface plasmons for a common six-fold hexagonal D-shaped PCF-SPR sensor. The causes of its sensing limitation is also investigated for better understanding of the modes in PCF. It is interesting that there is a secondary plasmon resonance peak existed that will have a significant impact on its sensing performance of system stability and accuracy, especially for analytes with high refractive index (RI = 1.42). 3. SPR Bio-sensor based on Dual Core D-Shaped PCF Embedded with Silver Nanowires for Multi-sensing. On the other hand, in order to increase the analyte sensing efficiency of the PCF-SPR biosensor, multi-sensing technique is brought into the sensor design as an efficient way to accelerate the detection processing time. In chapter 5, a novel dual-core D-shaped PCF based SPR biosensor with embedded silver nanowires is proposed for multi-sensing. This biosensor design can achieve two analytes detections simultaneously with high sensitivity and it also provides a broad sensing RI range which covers most of the refractive index values of already known viruses, proteins, DNAs (deoxyribonucleic acids)/RNAs (ribonucleic acids), antigens/antibodies. Moreover, with the innovative additional critical sensing channel, it helps the users to distinguish the analyte of interest with the corresponding sensing channel more easily. Whereas the other multi-channel sensing design can only show the sensing peaks in the loss spectra without any information about the location (channel) where the individual specific binding reaction takes place. 4. Modelling Instruction of a Common PCF-SPR Bio-sensor using COMSOL Multiphysics. As those three research projects are all based on the numerical analysis on COMSOL Multiphysics, a comprehensive modelling design flow based on COMSOL Multiphysics system about how to simulate a standard PCFSPR inner air hole metal-coating sensor was summarized and presented as an example to help anyone who will carry out the design process in a fast, simple and easy way (see Appendix A).
Supervisor: Kaliyaperumal, Nakkeeran ; Aphale, Sumeet Sponsor: University of Aberdeen
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Surface plasmon resonance ; Fiber optics