966 research outputs found
Design of microstructured fibers for hollow core guidance
Instead of the traditional index guidance, microstructured fibers can guide light in a core of refractive index lower than that of its cladding using mechanisms like photonic band gap guidance, inhibited coupling guidance and anti-resonant guidance. Their guidance is usually leaky and depends on the photonic properties of their structured cladding. Specifically, photonic band gap guidance is possible with photonic crystals, whose photonic band gaps appear below the refractive index index of the core. Guidance in a low-index core or hollow core guidance, is of interest for applications in the fields of bioanalytic, quantum gas, lasers and others that involve interacting of the light with confined matter of low refractive index. My work is aimed at investigating the possibility of hollow core guidance with an all-solid microstructured cladding. Ideally, such a hollow core waveguide is expected to have obvious guidance advantages over capillaries. Besides, it also surpasses the holey hollow core band gap fibers in the optofluidic applications by avoiding undesired penetration of the liquid into the cladding channels. To achieve the design of the ideal hollow core waveguide, I developed two models for all relevant modes in microstructured fibers: an analytical method with binary functions and a reflection-based planar model. While the binary functions for photonic band gap is more about ideal periodic structures extended into infinite, the reflection and transmission analysis with a reflection-based planar model is more practical to be used for waveguides with finite periodic structures and deliberately induced disorder
Development of Photonic Crystal Fiber Based Gas/ Chemical Sensors
The development of highly-sensitive and miniaturized sensors that capable of
real-time analytes detection is highly desirable. Nowadays, toxic or colorless
gas detection, air pollution monitoring, harmful chemical, pressure, strain,
humidity, and temperature sensors based on photonic crystal fiber (PCF) are
increasing rapidly due to its compact structure, fast response and efficient
light controlling capabilities. The propagating light through the PCF can be
controlled by varying the structural parameters and core-cladding materials, as
a result, evanescent field can be enhanced significantly which is the main
component of the PCF based gas/chemical sensors. The aim of this chapter is to
(1) describe the principle operation of PCF based gas/ chemical sensors, (2)
discuss the important PCF properties for optical sensors, (3) extensively
discuss the different types of microstructured optical fiber based gas/
chemical sensors, (4) study the effects of different core-cladding shapes, and
fiber background materials on sensing performance, and (5) highlight the main
challenges of PCF based gas/ chemical sensors and possible solutions
Specialty Photonic Crystal Fibres and Their Applications
This book is intended to provide an overview of the state-of-the-art in specialty photonic crystal fiber technology and its multiple applications, combined with an optimistic outlook to what lies ahead. It comprises six original research papers and one review from different leading research institutions worldwide
Enhanced spontaneous raman scattering and gas composition analysis using a photonic crystal fiber
Spontaneous gas-phase Raman scattering using a hollow-core photonic bandgap fiber (HC-PBF) for both the gas cell and the Stokes light collector is reported. It was predicted that the HC-PBF configuration would yield several hundred times signal enhancement in Stokes power over a traditional free-space configuration because of increased interaction lengths and large collection angles. Predictions were verified by using nitrogen Stokes signals. The utility of this system was demonstrated by measuring the Raman signals as functions of concentration for major species in natural gas. This allowed photomultiplier-based measurements of natural gas species in relatively short integration times, measurements that were previously difficult with other systems. © 2008 Optical Society of America
Selective Serial Multi-Antibody Biosensing with TOPAS Microstructured Polymer Optical Fibers
We have developed a fluorescence-based fiber-optical biosensor, which can selectively detect different antibodies in serial at preselected positions inside a single piece of fiber. The fiber is a microstructured polymer optical fiber fabricated from TOPAS cyclic olefin copolymer, which allows for UV activation of localized sensor layers inside the holes of the fiber. Serial fluorescence-based selective sensing of Cy3-labelled α-streptavidin and Cy5-labelled α-CRP antibodies is demonstrated
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Optofluidic Microreactors for Advanced Photocatalysis
This PhD project explores the application of hollow-core photonic crystal fibres (HC- PCFs) as a novel and advanced characterization technique to monitor photocatalysis. The use of HC-PCFs as the core element of a newly developed characterisation platform has many benefits: HC-PCF’s light-guiding abilities and low-loss properties make absorp- tion spectroscopy based screening of reaction intermediates at low sample concentrations possible. The photoreduction of methyl viologen by carbon nanodots (CNDs) was studied and compared to theory by modelling reaction pathways. Oxidation states of cobaloximes, that are currently employed as molecular catalysts for solar hydrogen generation, could be studied and analysed in different pH environments. Furthermore, a novel enzyme based photocatalyst was characterized and its application in photocatalysis explored. With the resulting new insight and understanding of the reaction kinetics and reaction pathways, these nanoscale photocatalytic systems can be improved further to increase conversion efficiency. A functionalisation of HC-PCFs by depositing gold nanoparticles on the core wall lays the foundation towards surface-enhanced Raman sensing of reaction interme- diates. Spatial light modulation (SLM) techniques are applied to excite a wide variety of higher-order modes with well-defined cross-sectional intensity distributions inside the HC-PCF’s core. An automated fast-switching between inverted higher-order modes can in the future be exploited to enable pump-probe and diffusion/ adhesion measurements.EPSRC, NanoDT
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