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This dissertation presents a fibre-optic sensing approach to provide continuous measurements of CO2 concentration at discrete points under typical conditions of geological CO2 storage. Carbon capture and storage is considered to have potential for a large-scale reduction in CO2 emissions in a relatively short period of time while other solutions to replace fossil fuels are being investigated. One significant drawback of carbon capture and storage is the possibility of long-term CO2 leakage. Therefore, the development of reliable technology for monitoring, verification, and accounting of geological CO2 storage is critical to fulfill safety regulations and achieve public acceptance. The major limitations of current technology include relatively low resolutions, high costs, and the lack of continuous monitoring for long periods of time. To address these limitations, two types of fibre-optic sensors are investigated, namely long period gratings and Mach-Zehnder interferometers. The sensing principle for CO2 detection is based on the sensitivity of these sensors to the refractive index of the medium that surrounds the fibre. Fibre-optic sensors are attractive for downhole applications due to the possibility of fabricating inexpensive high resolution devices that are able to operate in harsh environments over long periods of time. This dissertation focuses on increasing the refractive index sensitivity of long period gratings and Mach-Zehnder interferometers by applying coatings that have a high refractive index. The dip-coating method is used to coat long period gratings with polystyrene, and the sensitivity at low refractive indices is increased by tuning coating thickness. The results show that long period gratings coated with polystyrene are able to detect CO2 in gaseous and aqueous media. This work reports the first measurement of CO2 dissolution in water at high pressure with a fibre-optic sensor. Additionally, atomic layer deposition is investigated to coat long period gratings and Mach-Zehnder interferometers with hafnium oxide. The study of this coating technique aims to address the main limitation of the dip-coating method: the challenge to achieve precise control over coating thickness. The results show that atomic layer deposition is suitable to maximize the sensitivity of long period gratings and Mach-Zehnder interferometers at a target refractive index. / Graduate / 0548 / 0752 / 0799 / luismelo@uvic.ca

X-ray phase-contrast imaging has seen rapid development in recent decades due to its superior performance in imaging low-absorption objects, compared to traditional attenuation x-ray imaging. Having higher demand on coherence, x-ray phase-contrast imaging is performed mostly at synchrotrons. With the development of different imaging techniques, and the development of laboratory sources and x-ray optics, x-ray phase-contrast imaging can now be implemented on laboratory systems, which is promising and practical for broader range of applications. The subject of this thesis is the implementation, development and comparison of different laboratory phase-contrast methods using a liquid-metal-jet source. The three x-ray phase-contrast imaging methods included in this thesis are the propagation-, grating-, and speckle-based techniques. The grating-based method has been implemented on a laboratory system with a liquid-metal-jet source, which yields several times higher brightness than a standard solid-anode microfocus source. This allows shorter exposure time or a higher signal-to-noise ratio. The performance of the grating-based method has been experimentally and numerically compared with the propagation-based method, and the dose required to observe an object as a function of the object’s diameter has been investigated with simulations. The result indicates a lower dose requirement for the propagation-based method in this system but a potential advantage for the grating-based method to detect relatively large samples using a monochromatic beam. The speckle-based method, both the speckle-tracking and speckle-scanning techniques, has been implemented on a laboratory system for the first time, showing its adaptability to radiation of low temporal coherence. Tomography has been performed and shows the potential applications of this method on quantitative analysis on both absorption and phase information of materials. As a basis for further optimization and comparisons to other methods, the noise properties of the differential phase contrast of the speckle-based method have been studied and an analytical expression for the noise variance introduced, showing a similarity to the grating-based method. / Faskontrastavbildning med röntgenstrålning är en teknik som har utvecklats kraftigt de senaste årtiondena, eftersom den fungerar bättre än traditionella, absorptionsbaserade röntgenundersökningar för objekt med låg absorption. Den har dock höga krav på koherens, vilket gjort att den huvudsakligen används vid stora synkrotron-anläggningar. Tack vare utveckligen av nya avbildningstekniker, laboratoriekällor och röntgenoptik kan numera faskontrast användas även med laboratoriesystem, vilket är lovande då tekniken kan användas vid ett större antal olika tillämpningsområden Denna avhandling syftar till att tillämpa, utveckla och jämföra olika faskontrastmetoder i laboratoriemiljö, med en metallstråleröntgenkälla. De tre faskontrastmetoderna som behandlas i denna avhandling är propogation, gitter och speckelbaserad faskontrast. Den gitterbaserade metoden har implementerats i ett laboratoriesystem med en metallstrålekälla som ger flera gånger högre radians än en vanlig, fast mikrofokuskälla. Den högre radians en möjliggör kortare exponeringstider eller högre signal-brusförhållande. Den gitterbaserade tekniken har jämförts experimentellt och numeriskt med den propageringsbaserade metoden. Den strålningsdos som krävs för observera ett objekt, som funktion av dess diameter, har jämförts för de båda teknikerna, den här gången via simuleringar. Resultaten visar på en lägre strålningsdos för den propagationsbaserade tekniken i detta fall, men även att det finns en potentiell fördel för den gitterbaserade tekniken för något större objekt med monokromatisk röntgenstrålning. Speckelbaserade tekniker, nämare bestämt den som bygger på att spåra speckel och den som bygger på att scanna diffusorn, har för första gången implementerats i laboratoriemiljö. Därmed har visats att de fungerar även för strålning med låg tidskoherens. Tekniken har även använts för tomografi och visar möjliga tillämpningar inom kvantitativ analys av material. För att förenkla framtida optimeringar och jämförelser av tekniken med andra metoder, har brusegenskaperna för den speckelbaserade metoden studerats och visat sig likna den gitterbaserade metoden. / <p>QC 20160921</p>

This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations. The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials. The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer. From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform. With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors. / <p>QC 20141114</p>

Le domaine du spectre électromagnétique correspondant aux fréquences térahertz est encore peu exploité, pourtant, les applications nécessitant la génération, l’amplification ou la détection d’un signal térahertz sont nombreuses et intéressantes. Dans ce travail, nous nous intéressons tout particulièrement au détecteurs plasmoniques, qui constituent une alternative prometteuse à la montée en fréquence des capteurs électroniques et à l’utilisation de capteurs thermiques pour les photons de faible énergie. Les capteurs plasmoniques fonctionnent grâce au couplage entre le photon térahertz et un plasmon au sein d’un gaz d’électrons bidimensionnel (2DEG). Le plasmon-polariton est ensuite transformé en un signal continu et détectable. Nous utilisons pour cela le 2DEG présent dans l’hétérostructure AlGaN/GaN. Le couplage entre le photon et le plasmon-polariton est réalisé par un réseau métallique déposé sur la structure semi-conductrice. Tout d’abord, l’étude du couplage photon/plasmon par des simulations électromagnétiques nous a permis de connaître les fréquences de résonance des plasmons-polaritons en fonction des dimensions du réseau. Le motif de réseau composé de deux bandes de métal de largeurs différentes a été plus particulièrement étudié. Ce motif permettant aux détecteurs d’atteindre une très haute sensibilité [Coquillat et al., 2010] et n’avait pas encore été étudié du point de vue de son efficacité de couplage. Des détecteurs, dimensionnés pour notre montage de test à 0,65 THz, ont ensuite été fabriqués puis mesurés avec un réseau non-polarisé, à température ambiante et refroidis à l’azote. La correspondance entre la variation de la sensibilité en fonction de la fréquence et les spectres d’absorption mesurés au spectromètre infrarouge à transformée de Fourier (FTIR) montre l’importance de l’étape de couplage dans le processus de détection. Contrôler la densité électronique dans le 2DEG permet de modifier la fréquence de résonance des plasmons-polaritons et d’augmenter la sensibilité des détecteurs. Nous avons mené des développements technologiques de manière à pouvoir contrôler la densité électronique du 2DEG en appliquant une tension sur le réseau. Cette étape constitue un défi technologique compte tenu de la surface très étendue des réseaux (plusieurs mm²). Nous avons finalement fabriqué des détecteurs pour lesquels la fréquence de résonance de couplage peut être contrôlée grâce à la tension appliquée sur le réseau. / Abstract: The objectives of this thesis were the fabrication, the measurement and the study of gallium nitride THz detectors. These detectors are working as follows : first the incident THz photon is coupled to a plasmon in the quantum well at the interface AlGaN/GaN. This plasmon is then turned into a continuous measurable current. One of the key-components in this type of detectors is the grating coupling the incident photon and the plasmon. Electromagnetic simulations have been made to determine the dimensions of the grating depending on the detection frequency. Detectors were then fabricated using the precendently calculated grating patterns. Their working frequency depending on their dimensions were measured with a good agreement with the previously led simulations. The grating is not used only as coupling element, but can be used to monitor the electron density in the quatum well as well, what should allow an exaltation of the rectification phenomenon and a frequency tunability. A technological development was needed to achieve grating actually monitoring the electron density over a wide range. It was a real challenge to fabricate such wide grating (36 mm²) with such small periods (about one micrometer) using epitaxies developped for devices with a much smaller area.

[pt] A magnetostricção é a propriedade dos materiais ferromagnéticos de se deformarem pela presença de um campo magnético externo. Trata-se de uma propriedade inerente ao material, que não muda com o tempo. Materiais que apresentam deformações da ordem de 10-3 são conhecidos como materiais de magnetostricção gigante (GMM). Esta dissertação de mestrado estuda a aplicação destes materiais em sensores de deslocamento onde não há contacto entre o elemento cursor (um ímã) e o elemento sensor (GMM). O princípio de funcionamento consiste em aplicar um gradiente de campo magnético ao GMM que está fixo. O gradiente de campo magnético é gerado por um ímã preso ao componente ou estrutura na qual se quer medir o deslocamento. As variações no campo magnético no material GMM originados pelo deslocamento do ímã (estrutura), provocam uma deformação no GMM, que é detectada com extensômetros do tipo Strain Gauge ou Redes de Bragg. Neste trabalho apresenta-se a caracterização da deformação de GMM em relação a um campo constante aplicado, e análises do seu comportamento para diferentes geometrias. Efeitos de pressão, polarização com um segundo ímã, e diferentes gradientes de campo magnético são também estudados. É observado um comportamento local para a deformação quando a medida é realizada em diferentes regiões do GMM. Os resultados obtidos permitiram a medição de deslocamentos de alguns micra estando o elemento sensor a até 10 mm de distância do elemento cursor. / [en] Magnetostriction is a property of ferromagnetic materials to deform in the presence of a magnetic field. Magnetostriction is an inherent property of magnetic materials, which is unchangeable with time. Materials exhibiting strains in the order of 10-3 are known as giant magnetostrictive materials (GMM).In this dissertation we study the application of these materials in displacement sensors where there is not contact between the cursor element (magnet) and sensor element (GMM). Its principle of operation consists of applying a magnetic field gradient to a GMM located at a fixed position. The magnetic field gradient is produced by a magnet attached to the component or structure in which the displacement will be measured.The variation on the magnetic field in the GMM position originated from the displacement of the magnet, results in a strain in the GMM that can be detected with a Strain Gauge or Bragg Grating extensometers. In this work is presented the characterization of the strain on GMM cuboids against a constant magnetic field and the analysis of its behavior for different geometries. Effects of pressure, polarization with a second magnet, and different gradients of magnetic field are also studied. It is observed a local behavior for strains when it is measured in different regions of GMM cuboid. The results obtained allow us to measure displacements of about few micra when the sensor is at a distance of 10 mm from the cursor element.

Depuis la découverte des rayons X par Röntgen, l'imagerie radiographique utilise le contraste d'absorption. Cette technique est efficace uniquement si les objets à étudier sont suffisamment absorbants. C'est pour cela qu'on peut détecter une lésion osseuse avec une radiographie, mais pas une lésion ligamentaire.Toutefois, l'imagerie par contraste de phase peut permettre de surmonter cette limite. Depuis les années 2000, s'appuyant sur des travaux similaires existant en optique visible, les scientifiques des rayons X essayent de mettre au point des dispositifs sensibles au contraste de phase et compatibles avec des applications industrielles comme l'imagerie médicale ou le contrôle non-destructif. Néanmoins, les architectures classiques des interféromètres sont très difficiles à mettre en place dans les rayons X durs, et sont trop contraignantes pour être transférables vers l'industrie. C'est pourquoi des dispositifs utilisant des réseaux de diffraction ont été les plus développés. Ils ont permis d'obtenir les premières images de radiographie par contraste de phase sur des humains vivants.Mais les architectures proposées aujourd'hui utilisent plusieurs réseaux et son contraignantes pour les industriels. C'est pourquoi j'ai développé au cours de ma thèse un système n'utilisant qu'un unique réseau de phase. J'ai montré qu'un tel dispositif peut générer des interférogrammes achromatiques et invariants par propagation. Ce dispositif a permis d'effectuer des mesures de contraste de phase quantitatives sur un fossile biologique, ainsi que des mesures métrologiques sur des miroirs plans sensibles aux rayons X. / Since Röntgen discovered X-rays, X-ray imaging systems are based on absorption contrast. This technique is inefficient for weakly absorbing objects. As a result, X-ray standard radiography can detect bones lesions, but cannot detect ligament lesions.However, phase contrast imaging can overcome this limitation. Since the years 2000, relying on former works of opticians, X-ray scientists are developing phase sensitive devices compatible with industrial applications such as medical imaging or non destructive control.Standard architectures for interferometry are challenging to implement in the X-ray domain.This is the reason why grating based interferometers became the most promising devices to envision industrial applications. They provided the first x-ray phase contrast images of living human samples.Nevertheless, actual grating based architectures require the use of at least two gratings, and are challenging to adapt on an industrial product. So, the aim of my thesis was to develop a single phase grating interferometer. I demonstrated that such a device can provide achromatic and propagation invariant interference patterns. I used this interferometer to perform quantitative phase contrast imaging of a biological fossil sample and x-ray flat mirror metrology.

Ces travaux de thèse ont pour but d’analyser les outils de photolithographies permettant d’inscrire des réseaux des diffractions et d’identifier ceux qui sont suffisamment flexibles pour être adapté à des substrats non conventionnels tel que des cylindres ou des tubes. Les outils de photolithographies développés ont aussi été ajustés afin d’inscrire directement un réseau de diffraction dans une couche fonctionnelle de TiO2, apporté par la voie sol-gel. Cette thèse est une étude prospective car la périodicité ou le motif des structures diffractantes inscrites n’ont pas été définis pour une application spécifique. Deux outils de photolithographies ont été adaptés avec succès aux substrats cylindriques. Ils seront présentés ici et s’accompagneront d’une perspective en vue d’une application particulière. Enfin, le dernier chapitre se distincte des précédents car il ne porte pas sur le développement d’un outil de photolithographie mais sur la transformation chimique du TiO2 (diélectrique) en TiN (métal), il reste néanmoins dans la continuité de ses travaux de thèse car cette transformation est adaptée à tous types de substrats / The aim of this thesis is to analyze the photolithography tools used to print diffraction gratings and to identify those that are sufficiently flexible to be adapted to unconventional substrates such as cylinders or tubes. The photolithography tools developed have also been adjusted in order to write directly a diffraction grating in a functional layer of TiO2, supplied by the sol-gel pathway. This thesis is a prospective study because the periodicity or the pattern of the registered diffracting structures has not been defined for a specific application. Two photolithography tools have been successfully adapted to cylindrical substrates. They will be presented here and will be accompanied with a perspective for a specific application. Finally, the last chapter is distinct from the previous ones because it does not concern the development of a photolithography tool but on the chemical transformation of TiO2 (dielectric) into TiN (metal), it nevertheless remains in the continuity of its thesis because this transformation is adapted to all types of substrates

With 400 Gbps Ethernet being developed at the time of writing this thesis, all-optical networks are a solution to the increased bandwidth requirements of data communication allowing architectures to become increasingly integrated. High density integration of optical components leads to potential ‘Optical/Photonic’ electromagnetic compatibility (EMC) and signal integrity (SI) issues due to the close proximity of optical components and waveguides. Optical EMC issues are due to backscatter, crosstalk, stray light, and substrate modes. This thesis has focused on the crosstalk in Optical Add/Drop Multiplexers (OADMs) as an EMC problem. The main research question is: “How can signal integrity be improved and crosstalk effects mitigated in small-sized OADMs in order to enhance the optical EMC in all-optical networks and contribute to the increase in integration scalability?” To answer this question, increasing the crosstalk suppression bandwidth rather than maximizing the crosstalk suppression ratio is proposed in ring resonator based OADMs. Ring resonators have a small ‘real estate’ requirement and are, therefore, potentially useful for large scale integrated optical systems. A number of approaches such as over-coupled rings, vertically-coupled rings and rings with random and periodic roughness are adopted to effectively reduce the crosstalk between 10 Gbps modulated channels in OADMs. An electromagnetic simulation-driven optimization technique is proposed and used to optimize filter performance of vertically coupled single ring OADMs. A novel approach to analyse and exploit semi-periodic sidewall roughness in silicon waveguides is proposed. Grating-assisted ring resonator design is presented and optimized to increase the crosstalk suppression bandwidth.

In the pursuit of economical and rapid fabrication solutions on the micro and nano scale, polymer replication has proven itself to be a formidable technique, which despite zealous development by the research community, remains full of promise. This thesis explores the potential of elastomers in what is a distinctly multidisciplinary field. The focus is on developing innovative fabrication solutions for planar photonic devices and for nanoscale devices in general. Innovations are derived from treatments of master structures, imprintable substrates and device applications. Major contributions made by this work include fully replicated planar integrated optical devices, nanoscale applications for photolithographic standing wave corrugations (SWC), and a biologically templated, optical fiber based, surface-enhanced Raman scattering (SERS) sensor. The planar devices take the form of dielectric rib waveguides which for the first time, have been integrated with long-period gratings by replication. The heretofore unemployed SWC is used to demonstrate two innovations. The first is a novel demonstration of elastomeric sidewall photolithographic mask, which exploits the capacity of elastomers to cast undercut structures. The second demonstrates that the corrugations themselves in the absence of elastomers, can be employed as shadow masks in a directional flux to produce vertical stacks of straight lines and circles of nanowires and nanoribbons. The thesis then closes by conceptually combining the preceding demonstrations of waveguides and nanostructures. An optical fiber endface is em ployed for the first time as a substrate for patterning by replication, wherein the pattern is a nanostructure derived from a biological template. This replicated nanostructure is used to impart a SERS capability to the optical fiber, demonstrating an ultra-sensitive, integrated photonic device realized at great economy of both time and money, with very real potential for mass fabrication.