abstract: Current organic light emitting diodes (OLEDs) suffer from the low light extraction efficiency. In this thesis, novel OLED structures including photonic crystal, Fabry-Perot resonance cavity and hyperbolic metamaterials were numerically simulated and theoretically investigated. Finite-difference time-domain (FDTD) method was employed to numerically simulate the light extraction efficiency of various 3D OLED structures. With photonic crystal structures, a maximum of 30% extraction efficiency is achieved. A higher external quantum efficiency of 35% is derived after applying Fabry-Perot resonance cavity into OLEDs. Furthermore, different factors such as material properties, layer thicknesses and dipole polarizations and locations have been studied. Moreover, an upper limit for the light extraction efficiency of 80% is reached theoretically with perfect reflector and single dipole polarization and location. To elucidate the physical mechanism, transfer matrix method is introduced to calculate the spectral-hemispherical reflectance of the multilayer OLED structures. In addition, an attempt of using hyperbolic metamaterial in OLED has been made and resulted in 27% external quantum efficiency, due to the similar mechanism of wave interference as Fabry-Perot structure. The simulation and optimization methods and findings would facilitate the design of next generation, high-efficiency OLED devices. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

The thesis deals with a design of a comparing interferometer. It concerns a setup of two interferometers, one of them is a Michelson and another a Fabry-Pérot type. This set-up is made to compare results of length measurements simultaneously performed by each of them. In the Theory, basic principles of Michelson and Fabry-Pérot interferometers are described. A special attention is paid to an innovative method of length measurement with tunable lasers and optical frequency comb. In the Practical Part, so-called Pilot Experimental Setup is described. It is a prototype that has been used to perform basic experiments on comparing of the two above mentioned methods. Based on experimental results and practical experience with the Pilot Experimental Setup, a Final Setup is designed. It comes in a form of a stand-alone instrument.

QC 20101206

No description available.

Absorption plays a critical role in a variety of optical applications – sometimes it is desirable to minimize it as in optical fibers and waveguides, or to enhance it as in solar cells and photodetectors. We describe here a new optical scheme that controllably produces high optical absorption over a broad wavelength range (hundreds of nm) in systems that have low intrinsic absorption over the same range. This effect, 'coherent perfect absorption' or CPA, arises from a subtle interplay between interference and absorption of two beams incident on a weakly absorbing medium. In the first part of this study, we present an analytical model that captures the relevant physics of CPA in one-dimensional photonic structures. This model elucidates an absorption-mediated interference effect that underlies CPA – an effect that is normally forbidden in Hermitian systems, but is allowed when conservation of energy is violated due to the inclusion of loss. As a concrete example, we consider a Fabry-Pérot resonator containing a lossy dielectric and confirm this model through a computational study of a 1-micron-thick silicon layer in a cavity formed of dispersive mirrors with aperiodic multilayer design. We confirm that one may achieve 100% absorption in this thin silicon layer (whose intrinsic absorption is only ~ 3%) in the near-infrared. We then design two device models using few-micron-thick aperiodic planar dielectric mirrors and demonstrate (computationally, as well as experimentally) spectrally flat, coherently enhanced absorption at the theoretical limit in a 2-micron-thick film of polycrystalline silicon embedded in symmetric and asymmetric cavities. This coherent effect is observed over an octave-spanning wavelength range of ~800 – 1600 nm utilizing incoherent light in the near-infrared, exploiting mirrors that have wavelength-dependent reflectivity devised to counterbalance the decline in silicon's intrinsic absorption at long wavelengths. We anticipate that the design principles established here may be extended to other materials, broader spectral ranges, and large surface areas. Finally, we study the effect of the angle of incidence on CPA in planar structures. The results of this study point to a path for realizing CPA in such systems continuously over large bandwidths.

During the past decades, femtosecond laser micro-fabrication has gained growing interests owing to its several unique features including direct and maskless fabrication, flexible choice of materials and geometries, and truly three-dimensional fabrication. Moreover, fiber-optic sensors have demonstrated distinct advantages over traditional electrical sensors such as the immunity to electromagnetic interference, miniature footprint, robust performance, and high sensitivity. Therefore, the marriage between femtosecond laser micro-fabrication and optical fibers have enabled and will continue to offer vast opportunities to create novel structures for sensing applications. This dissertation focuses on design, fabrication and characterization of optical-fiber based interferometric devices for sensing applications. Three novel devices have been proposed and realized, including point-damage-based Fiber Bragg gratings in single-crystal sapphire fibers, all-sapphire fiber-tip Fabry-Pérot cavity, and in-fiber Whispering-Gallery mode resonator / Doctor of Philosophy / Optical fibers are an optical platform with cylindrical symmetry with overall diameter typically within 50 to 500 μm. The miniature footprint and large aspect ratio make it attractive in sensing applications, where intrusion, flexibility, robustness and small size are key design parameters. Beyond that, fiber-optic sensors also possess distinct operational advantages over traditional electrical sensors such as high sensitivity, immunity to electromagnetic interference (EMI), and fully distributed deployment. Owing to the above advances, fiber-optic sensors have been one of the key technologies in the broader sensing field for the past decades. However, the unique cylindrical shape of optical fiber makes it naturally less compatible to those well-developed fabrication technologies in the current sophisticated semiconductor industry. During the past decades, the possibility of three-dimensional (3D) writing inside transparent materials with tightly focused ultrafast laser pulses has attracted attention widely among the academy as well as the industry. Therefore, the marriage between ultrafast laser micro-fabrication and optical fibers have enabled and will continue to offer vast opportunities to create novel structures for sensing applications. This dissertation focuses on design, fabrication and characterization of optical-fiber based interferometric devices for sensing applications. Three novel devices have been proposed and realized, including point-damage-based Fiber Bragg gratings in single-crystal sapphire fibers, all-sapphire fiber-tip Fabry-Pérot cavity, and in-fiber Whispering-Gallery mode resonator.

In this thesis, we report the development of two types of optical sensors, one for high temperature pressure measurements and the other for real-time particle detection. With a high melting temperature (over 2000°C), low optical loss, and excellent corrosion resistance, sapphire (α-Al₂O₃) is ideal for high temperature sensing applications. Fabry-Perot (FP) cavity with optical interrogation of pressure response. The prototype is based on an extrinsic FP interferometer design and is constructed by combining reactive ion etching (RIE) with direct wafer bonding. Long-term testing proves that the adhesive-free wafer bond is sufficient to create a sealed Fabry-Perot cavity as a pressure transducer. Pressure measurement over a range of 6 to 200 psi has been demonstrated at room temperature using white-light interferometry. For the other sensor, the goal is to detect the presence of micro- and nanoparticles in real time. The sensor is based on a silica fiber taper, and we aim to detect particle presence by measuring optical scattering and absorption induced by particles attached to the taper surface. To establish the relationship between particle density and optical transmission loss, we first consider a model where Au nanospheres are self-assembled on taper surface through electrostatic interaction. An analytical model is established to describe the adsorption of gold nanospheres onto cylindrical and spherical silica surfaces from quiescent aqueous particle suspensions. The curved surfaces of the fiber taper and microspheres are coated with nm-thick layer of a polycation, enabling irreversible adsorption of the negatively charged spheres. Our results fit well with theory, which predicts that the rates of particle adsorption will depend strongly on the surface geometry. In particular, adsorption is significantly faster on curved than on planar surfaces at times long enough that the particle diffusion length is large compared to the surface curvature. This is of particular importance for plasmonic sensors and other devices where particles are deposited from a suspension onto surfaces which may have non-trivial geometries. We have established a theoretical model that can describe optical loss generated by particles on taper surface. This theory is validated by measuring, in real time, optical loss during the self-assembly of gold nanoparticles. We find that the measured optical loss can be quantitatively explained by the presence of multiple guided modes within the fiber taper region. Based on this work, we incorporate a fiber taper into a cascade impactor and show that welding aerosols attached to the fiber taper surface can induce measurable transmission loss during the welding process. / Ph. D.

La Enfermedad de Fabry (EF) tiene su origen en las mutaciones del gen GLA, localizado en el cromosoma X, que provocan una enfermedad rara lisosomal a causa de la reducción de la actividad de la enzima alfa-galactosidasa A. Como consecuencia se origina esta patología progresiva y multisistémica caracterizada, fundamentalmente, por manifestaciones renales, cardiovasculares, cutáneas y cerebrovasculares en diferente grado. Se estima que la incidencia real de esta patología está se encuentra infradiagnosticada, sobre todo en mujeres. El Asesoramiento o Consejo Genético contribuye a aliviar la incertidumbre y el sentimiento de vulnerabilidad que puede surgir ante el diagnóstico de la enfermedad, así como a la adaptación ante la condición genética familiar. En este sentido, estudios realizados en otras patologías como es el cáncer de mama familiar indican que el Asesoramiento Genético no sólo confirma el diagnóstico clínico y, en ocasiones, el pronóstico de ésta, sino que también permite identificar a los portadores en la familia mediante estudios genéticos directos y los riesgos para su descendencia. De este modo, la incorporación del Asesoramiento Genético en el sistema asistencial puede producir una mejora de la calidad de vida y en la prevención clínica de los pacientes. Estas intervenciones han sido estudiadas mediante el empleo de encuestas directas al paciente, las cuales captan la experiencia hacia el sistema de salud. Una de estas encuestas, GCOS-24, ha sido adaptada y validada para el Asesoramiento Genético como herramienta de medida del potencial de estas intervenciones basada en el Modelo de la Teoría del Control Personal Percibido o empoderamiento. La presente Tesis se basa en el análisis de la influencia que tiene el Consejo Genético en una población compuesta por 64 afectos de EF, pertenecientes a dos entornos bien diferenciados. El objetivo general planteado para esta tesis fue estudiar los factores que desencadenaban la toma de decisiones sobre comportamientos preventivos en salud en EF, así como si finalmente los pacientes habían llevado a cabo estas acciones. Las intervenciones de Asesoramiento Genético de manera estructurada y dirigida en un entorno clínico controlado en pacientes con EF aumentaba tanto el Control de decisión (p = 0,015), así como el Control cognitivo (p = 0,024). Esto conducía a una mayor toma de decisiones y participación en las acciones de salud preventivas; principalmente en cribado genético familiar (p < 0,001). Se ha comprobado que el aumento de participación en el cribado genético familiar incrementa la identificación de portadores –especialmente mujeres– anticipándose, de esta manera, a la aparición clínica de daños orgánicos irreversibles. Las intervenciones de Asesoramiento Genético de manera estructurada y dirigida en un entorno clínico controlado en pacientes con EF aumentaba tanto el Control de decisión (p = 0,015), así como el Control cognitivo (p = 0,024). Esto conducía a una mayor toma de decisiones y participación en las acciones de salud preventivas; principalmente en cribado genético familiar (p < 0,001). Se ha comprobado que el aumento de participación en el cribado genético familiar incrementa la identificación de portadores –especialmente mujeres– anticipándose, de esta manera, a la aparición clínica de daños orgánicos irreversibles.

Ce mémoire présente une nouvelle méthode permettant de caractériser la phase spectrale d'impulsions courtes se propageant dans de la fibre optique. L'information sur la phase des impulsions est extraite de l'analyse du signal temporel généré par l'interférence entre deux bandes spectrales sélectionnées par un réseau de Bragg. L'accord du réseau de Bragg, par l'application d'une contrainte sur la fibre optique, permet de déterminer la phase relative de toutes les composantes spectrales. Afin d'obtenir une bonne résolution spectrale, le réseau de Bragg est constitué d'une structure de type Fabry-Perot distribué qui transmet deux bandes spectrales distinctes selon la polarisation du signal indicent. Nous traitons le cas d'une modulation en amplitude périodique du signal analysé, avec une validation expérimentale, et nous menons des simulations pour une modulation en amplitude pseudoaléatoire. Nous discutons des limites de cette méthode de caractérisation et nous mettons en évidence l'importance de bien contrôler la polarisation du signal incident. Finalement, nous expliquons pourquoi cette méthode ne s'applique pas à une modulation en amplitude pseudo-aléatoire.

Die vorliegende Arbeit umfasst die Entwicklung einer neuartigen Drucksonde, welche die faseroptischen Sensortypen Fabry-Pérot-Interferometer und Faser-Bragg-Gitter als Hybridsensor kombiniert und minimalinvasiv im Gefäßsystem oder Hohlorganen platziert werden soll. Die simultane Auswertung aller Sensoren ermöglicht die Erfassung des räumlich und zeitlich verteilten Druckes. Die diagnostische Relevanz der Hybridsonde zur Analyse von Stenosen wird an den Krankheitsbildern der koronaren Herzkrankheit und der lumbalen Spinalkanalstenose aufgezeigt. Anhand von experimentellen in vitro Untersuchungen sowie eines in vivo Tierversuches wird die Leistungsfähigkeit der Hybridsonde zur verteilten Druckmessung evaluiert sowie das Potential der Neuentwicklung in der medizinischen Diagnostik bestätigt. Ausgehend von den gewonnen klinischen Daten wird eine Entwicklungsperspektive für ein Medizinprodukt zur minimalinvasiven Diagnostik aufgezeigt.:Abkürzungs- und Formelzeichenverzeichnis ix Vorwort 1 1. Einleitung 3 2. Medizinische Grundlagen 9 3. Technische und physikalische Grundlagen 23 4. Referenzdrucksensor 47 5. Faseroptische Hybridsonde 85 6. In vivo Tierversuch 115 7. Erkenntnisgewinn 135 8. Zusammenfassung und Ausblick 143 Anhang 147 Literaturverzeichnis 159 Abbildungsverzeichnis 175 Tabellenverzeichnis 179 Thesen 181 / This thesis presents the development of a novel pressure probe combining a fiber optic Fabry-Pérot-Interferometer and Fiber Bragg Gratings as a hybrid probe. The application is minimally invasive manometry of the vascular system as well as hollow organs. The simultaneous evaluation of several pressure reading points enables the detection of spatially and temporally distributed pressure. The diagnostic relevance of the hybrid probe for the analysis of stenoses severity is demonstrated at the application for coronary heart disease and lumbar spinal stenosis. By means of experimental in vitro investigations as well as an in vivo animal trial the hybrid probe's performance for distributed pressure sensing is assessed. Furthermore, this confirms the potential of the new development for medical diagnostics. Based on the clinical data obtained, a development perspective for a medical device for minimally invasive diagnostics is presented.:Abkürzungs- und Formelzeichenverzeichnis ix Vorwort 1 1. Einleitung 3 2. Medizinische Grundlagen 9 3. Technische und physikalische Grundlagen 23 4. Referenzdrucksensor 47 5. Faseroptische Hybridsonde 85 6. In vivo Tierversuch 115 7. Erkenntnisgewinn 135 8. Zusammenfassung und Ausblick 143 Anhang 147 Literaturverzeichnis 159 Abbildungsverzeichnis 175 Tabellenverzeichnis 179 Thesen 181