Near Infrared Characterization of Hetero-Core Optical Fiber SPR Sensors Coated with Ta2O5 Film and Their Applications

This paper describes the characteristics of optical fiber sensors with surface plasmon resonance (SPR) at 1,310 nm in which the scattering loss of silica optical fiber is low. SPR operation in the infrared wavelength range is achieved by coating a thin tantalum pentaoxide (Ta2O5) film. The novelty of this paper lies in the verification of how the hetero-core scheme could be operated as a commercial base candidate in the sense of easy fabrication, sufficient mechanical strength, and significant sensitivity as a liquid detector under the basis of a low loss transmission network in the near infrared wavelength region. The effect of Ta2O5 layer thickness has been experimentally revealed in the wavelength region extending to 1,800 nm by using the hetero-core structured optical fiber. SPR characterizations have been made in the wavelength region 1,000–1,300 nm, showing the feasible operation at the near infrared wavelength and the possible practical applications. In addition, the technique developed in this work has been interestingly applied to a multi-point water-detection and a water-level gauge in which tandem-connected SPR sensors system using hetero-core structured fibers were incorporated. The detailed performance characteristics are also shown on these applications

Reflectance-based low-cost disposable optical fiber surface plasmon resonance probe with enhanced biochemical sensitivity

A reflectance-based surface plasmon resonance (SPR) fiber sensor with enhanced sensitivity for biochemical sensing is reported after comparing its result with the transmittance-based SPR optical fiber sensors. The fabricated SPR sensor contains a gold-coated multimode fiber with the implementation of a standard source-sensor-spectrometer interrogation system. As the refractive index of the liquid under test is increased, a redshift of the SPR is observed. The coupling of the source to the fiber sensor is optimized by investigating the effect of an intentional misalignment in transmission-based setup. When a fiber tip coated with the silver mirror and the bifurcated fiber bundle is used, an alignment-free disposable sensor probe is achieved. A comprehensive characterization of the proposed reflectance-based SPR probe is discussed. The maximum sensitivity of 3212.19  nm/refractive index unit (RIU) is obtained

Studies on Sensor Networks with Fiber Optics for Agricultural Environment Monitoring

創価大

A numerical approach into new designs for SPR sensors in D-type optical fibers

This thesis investigates how to improve the performance of current designs of optical fiber sensors based on Surface Plasmon Resonance, and how to use a better understanding of the physical and sensing principles behind them to propose new sensing concepts and ideas. We adopt a methodology based on numerical simulations because they provide a better insight onto the operation of these sensors and because they allow an easy and quick way of testing new designs and concepts without the need to fabricate the sensors. We also show that these simulations have a good agreement with experimental results. We adopt a systematic approach to investigate the various parameters that influence the sensor performance, and present different sensors designs, where we study the localization, optical properties, shape and size of the metal components, combined with different type of fibers, resulting in the coupling between the plasmon and optical modes. Furthermore, we verify that choosing the optical modes used in sensing in multimode fibers can also have advantages. We investigate the use of modern artificial materials, such as metamaterials, as well as the inclusion of multiple wires in the fiber to enhance the performance of the SPR sensor. At a more fundamental level, we show that the control of the coupling between multiple plasmon modes in metal components and the optical modes in the fiber constitutes a new way to improve the performance of the sensor and can be inclusively used to develop a new type of SPR sensors capable of measuring simultaneously two variables, such as the external refractive index and temperatureEsta tese investiga como é possível melhorar o desempenho das estruturas atuais dos sensores de fibra ótica baseados em Ressonância Plasmónica de Superfície (SPR), bem como compreender melhor os princípios físicos e de sensorização na base do seu funcionamento, permitindo propor novos conceitos de sensores. Foi utilizada uma metodologia baseada em simulações numéricas, pois proporcionam um melhor entendimento do funcionamento desses sensores, constituindo uma maneira simples e rápida de testar novas estruturas e conceitos, sem a necessidade de fabricar os sensores. Mostra-se também que essas simulações têm uma boa concordância com os resultados experimentais. Foi adotada uma abordagem em que se investiga sistematicamente os diversos parâmetros que influenciam o desempenho do sensor e se apresentam diferentes estruturas de sensores onde foram estudadas a localização, propriedades óticas, forma e tamanho dos componentes metálicos, combinados com diferentes tipos de fibras, resultando no acoplamento entre os modos plasmónicos e os modos óticos. Também foi verificado que a escolha dos modos óticos utilizados na deteção em fibras multimodo pode apresentar vantagens. Foi investigado ainda o uso de materiais artificiais recentemente desenvolvidos, de que são exemplo os metamateriais, bem como, a inclusão de múltiplos fios metálicos na fibra, de forma a melhorar o desempenho dos sensores SPR. A um nível mais fundamental, foi demonstrado que o controlo do acoplamento entre os múltiplos modos plasmónicos gerados nos componentes metálicos e os modos óticos propagados na fibra constitui uma nova forma de melhorar o desempenho do sensor. Tal pode ser inclusivamente utilizado para desenvolver um novo tipo de sensores SPR capazes de medir simultaneamente duas variáveis, como por exemplo o índice de refração externo e a temperatura

Surface plasmon resonance sensing: an optical fibre based SPR platform with scattered light interrogation

This thesis describes the development, fabrication and optimisation of a Surface Plasmon Resonance (SPR) sensing architecture based on optical fibres. Motivated by biosensing applications, SPR was chosen as a simple and sensitive label-free technique that allows real time quantitative measurements of biomolecular interactions. Unlike conventional fibre SPR probes, this platform utilises a novel interrogation mechanism based on the analysis of scattered radiation facilitated by a rough plasmonic coating. A theoretical study is performed in order to determine the optimal parameters of the sensing configuration, i. e. the metal coating and fibre material. This analysis revealed a trade-off between the sensitivity of these devices, and their resolution. Optical fibres with cores made of lower refractive index materials were found to increase the sensitivity of the sensor, but broaden the SPR spectral signature. This broadening of the linewidth results in an unwanted increase in the sensor resolution, which leads to an undesirable increase in the detection limit. Therefore, experiments were performed to investigate the trade off between the sensitivity and resolution of the sensor to optimise both performance characteristics. The experimental demonstration and characterisation of a scattering SPR platform based on lead silicate fibres is described. The plasmonic coating with required surface roughness was fabricated using chemical electroless plating. In order to increase the refractive index sensitivity, a fibre SPR sensor with a lower refractive index core made of fused silica was produced. Due to the different surface properties of the silica glass and the lead silicate glass, surface modification with stannous chloride was required to fabricate suitable plasmonic coatings on the fused silica fibres. Characterisation of the new fused silica SPR sensors showed that the sensitivity of the sensing probe was improved, however, the spectral linewidth of the SPR signature was broadened, in agreement with the theoretical modelling. Nevertheless, analysis of the capability of the silica fibre based SPR sensors demonstrated potential for this platform in biological studies. To improve the resolution without affecting the sensitivity of a sensor, smaller core fibres can be used. However, using conventional small core fibres or fibre tapers is challenging due to their fragility and the requirement for fibre post processing to access the core. To overcome these difficulties, an SPR sensor based on a silica microstructured optical fibre with a core exposed along the entire fibre length was fabricated. Exposed Core Fibres (ECFs) have small cores that are supported by thin struts inside of a larger support structure, providing mechanical robustness to the fibre. The ECF SPR sensing platform doubled the improvement in the spectral linewidth when compared to the large core fused silica fibre sensor, without compromising sensitivity. Finally, the demonstration of Metal Enhanced Fluorescence (MEF) phenomena is presented. The effect of rough metallic coatings on the enhancement of fluorescence emission is investigated in planar glass substrates, showing significant improvement in emission when compared to smooth metal films. An optical fibre based MEF platform was demonstrated to illustrate the potential of rough metal coatings on a fibre for surface enhanced optical phenomena. This work is the first systematic study of a scattering based SPR sensing platform. This architecture addresses existing practical limitations associated with current SPR technologies, including but not limited to bulk design and affordability. Additionally, performance enhancement of the sensing probes is achieved through the use of alternative fibre material and geometry. The demonstrated performance improvements are not class-leading compared to commercial biosensing devices, however, the performance is in agreement with the theoretical analysis which provides a pathway for further improvement. This demonstrated that the scattering based SPR fibre platform is a practical new approach that offers the advantages of high sensitivity and signal to noise ratio, and low resolution, with the capability to improve the detection limit of SPR devices. Most importantly, this novel SPR interrogation approach allows the incorporation of two different sensing techniques, SPR and fluorescence, in the same fibre device, which opens pathways for novel biosensing applications combining the two phenomena.Thesis (Ph.D.)--University of Adelaide, School of Physical Sciences, 2017

Novel Specialty Optical Fibers and Applications

Novel Specialty Optical Fibers and Applications focuses on the latest developments in specialty fiber technology and its applications. The aim of this reprint is to provide an overview of specialty optical fibers in terms of their technological developments and applications. Contributions include:1. Specialty fibers composed of special materials for new functionalities and applications in new spectral windows.2. Hollow-core fiber-based applications.3. Functionalized fibers.4. Structurally engineered fibers.5. Specialty fibers for distributed fiber sensors.6. Specialty fibers for communications

Graphene-based hybrid materials: synthetic approaches and properties

Carbon has a unique chemistry reflected in its wide presence in the inorganic and organic world - benzene, diamond, graphite, fullerene, carbon nanotubes and now graphene - carbon seems to be at the centre of action in the playground of scientific research. In this review, synthesis and unique properties of graphene and graphene-based composites have been discussed with particular emphasis on the environmentally benign (green) synthetic methods and their wide applications, especially in energy conversion, energy storage, electronics, biomedical and biosensing applications

Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

Thanks to their unique attributes, such as good sensitivity, selectivity, high surface-to-volume ratio, and versatile optical and electronic properties, fluorescent-based bioprobes have been used to create highly sensitive nano -biosensors to detect various biological and chemical agents. These sensors are superior to other analytical instrumentation techniques like gas chromatography, high-performance liquid chromatography, and capillary electrophoresis for being biodegradable, eco-friendly, and more economical, operational, and cost-effective. Moreover, several reports have also highlighted their application in the early detection of biomarkers associ-ated with drug-induced organ damage such as liver, kidney, or lungs. In the present work, we comprehensively overviewed the electrochemical sensors that employ nanomaterials (nanoparticles/colloids or quantum dots, carbon dots, or nanoscaled metal-organic frameworks, etc.) to detect a variety of biological macromolecules based on fluorescent emission spectra. In addition, the most important mechanisms and methods to sense amino acids, protein, peptides, enzymes, carbohydrates, neurotransmitters, nucleic acids, vitamins, ions, metals, and electrolytes, blood gases, drugs (i.e., anti-inflammatory agents and antibiotics), toxins, alkaloids, antioxidants, cancer biomarkers, urinary metabolites (i.e., urea, uric acid, and creatinine), and pathogenic microorganisms were outlined and compared in terms of their selectivity and sensitivity. Altogether, the small dimensions and capability of these nanosensors for sensitive, label-free, real-time sensing of chemical, biological, and pharma-ceutical agents could be used in array-based screening and in-vitro or in-vivo diagnostics. Although fluorescent nanoprobes are widely applied in determining biological macromolecules, unfortunately, they present many challenges and limitations. Efforts must be made to minimize such limitations in utilizing such nanobiosensors with an emphasis on their commercial developments. We believe that the current review can foster the wider incorporation of nanomedicine and will be of particular interest to researchers working on fluorescence tech-nology, material chemistry, coordination polymers, and related research areas