The detection of high-energy neutrinos in the E > O(PeV) range requires newdetection techniques in order to cope with the decreasing flux. The radio detectionmethod uses Askaryan emission to detect these neutrinos. The propagation of theradio pulses has to be modeled carefully in order to estimate the properties of theneutrinos from the detected radio pulse. This report introduces a model whichwas implemented to the NuRadioMC code to simulate birefringence effects in theice of the South Pole. To do that, a new ice model was created which combinesthe density and directional dependence on the refractive index. With this icemodel and an analytical ray tracer the time delay and polarization resulting frombirefringence was simulated for different geometries. A directional dependenceon the magnitude of the time delay and the change of the polarization along thepropagation path was found. To model the mixing of the polarization states dueto this change in polarization a pulse propagation model was introduced. Timedelay calculations resulting from this model were compared to simulations andmeasurements from the ARA experiment and have shown good agreement.

Les nanoparticules de fluorures dopées avec des ions lanthanides ont connu un développement croissant ces dernières années. Elles présentent en effet des propriétés optiques d’upconversion remarquables et très intéressantes pour de multiples applications allant du photovoltaïque à l’imagerie médicale. Dans cette thèse, on a élaboré des nanobâtonnets de NaYF4 dopés Yb/Er/Gd, aux propriétés d’émission optimisées. Leur alignement par un champ électrique a ensuite été étudié, nous permettant de tirer parti de leur anisotropie et des propriétés physiques en découlant : biréfringence et luminescence polarisée.Les nanocristaux sont synthétisés par voie solvothermale, à haute température (200 °C) et sous haute pression (20 bars). Leur morphologie et leur structure cristalline sont contrôlées par un choix approprié des paramètres de synthèse comme le dopage en gadolinium ou les conditions de chauffage. A l’issue de la synthèse, l’état d’agrégation des particules de NaYF4 produites limite leur dispersion dans les solvants organiques usuels. Une fonctionnalisation bien spécifique avec des ligands possédant des groupements carboxylate ou phosphonate se révèle alors indispensable. Le greffage des particules avec un ion citrate ou une molécule d’alendronate permet d’obtenir des suspensions colloïdales très stables dans le DMSO. Par ailleurs, la réactivité de l’amine porté par l'alendronate nous a permis de greffer une deuxième molécule active : une rhodamine B, un colorant test, ainsi qu’un cristal liquide cyanobiphényl à tête carboxylique. Grâce à cette fonctionnalisation, de nouveaux matériaux hybrides organo-minéraux ont été développés. La réponse électro-optique des suspensions colloïdales soumises à un champ électrique haute fréquence suit une loi de type effet Kerr, avec une relation quadratique entre la biréfringence induite et l’amplitude du champ appliqué. Les constantes de Kerr sont de l’ordre de 10 8 m/V2 en cohérence avec ce qui a été observé sur d’autres systèmes. La biréfringence observée est majoritairement induite par la structure cristalline anisotrope des particules. Le mécanisme de réorientation de nos particules sous champ est largement dominé par la polarisation de leur nuage électronique. Une luminescence polarisée est finalement décrite, ouvrant la voie à l’usage des nanobâtonnets de NaYF4 comme sondes d’orientation dans des systèmes biologiques ou au sein de fluides en écoulement. / Fluorides nanoparticles doped with lanthanides have seen an increase in interest the last years. They offer outstanding optical properties with a very attractive upconversion for multiple applications from photovoltaics to medical imaging. In this work, we use NaYF4 nanorods doped with Yb/Er/Gd and optimized emission properties. Their alignment by an electric field allows us to access their anisotropic physical properties like polarized luminescence and birefringence.Nanocrystals are synthesized by a hydrothermal route, at high temperature (200 °C) and high pressure (20 bar). Morphology and crystalline structure can be controlled by varying gadolinium doping and heating conditions. At the end of the synthesis, the aggregation of the particles limits their dispersion in all common organic solvents. A particular functionalization with ligands having carboxylate or phosphonate functions is shown to be necessary. The grafting of particles with ions like citrate or alendronate allows to obtain very stable colloidal suspensions in DMSO. Furthermore, the reactivity of the amine function carried by alendronate enables us to graft a second active dye like rhodamine B or a cyanobiphenyl liquid crystal with a carboxylic group. New organo-mineral materials can be produced with this functionalization. The electro-optical response of colloidal suspensions submitted to a high-frequency electric field follows the Kerr law, with a quadratic relation between induced birefringence and the amplitude of the applied field. The system exhibits Kerr constants of the order of 108 m/V2, in agreement with the literature. The birefringence is induced by the anisotropic crystalline structure of the colloid, not by its shape. The mechanism of reorientation of colloids under an electric field is widely dominated by the polarization of their ionic cloud. A polarized luminescence is finally described, which will allow the use of NaYF4 nanorods as orientation probes in biological systems or fluid flows.

No description available.

No description available.

The detection of high-energy neutrinos in the EeV range requires new detection techniques to cope with the small expected flux. The radio detection method, utilizing Askaryan emission, can be used to detect these neutrinos in polar ice. The propagation of the radio pulses has to be modeled carefully to reconstruct the energy, direction, and flavor of the neutrino from the detected radio signals. This thesis outlines the effect of birefringence in ice, which splits up the radio pulse into two orthogonal polarization components with slightly different propagation speeds. The signatures resulting from birefringence can help to reconstruct the energy and direction of the neutrino. In this thesis, the effect of birefringence is derived from first principles where the only free parameter of the model is the dielectric tensor as a function of depth and direction. The introduced model can propagate full RF waveforms which for the first time allows for the accounting of interference due to changing polarization eigenvectors during propagation. The model is available open-source through the NuRadioMC framework. The predictions of the model are compared to in-situ calibration data from the ARA and ARIANNA experiments and the implications for neutrino detection are discussed. / Detektionen av högenergetiska neutriner inom EeV-intervallet kräver nya detektionsmetoder för att handskas med flödet av neutriner, som förväntas vara mycket lågt. Radiodetektormetoden, som nyttjar Askaryanemission, kan användas för att detektera dessa neutriner i polarisarna. Radiopulsernas propagering måste modelleras noggrant för att rekonstruera energin, riktningen och smaken av neutrinon från detektorns radiosignaler. Denna avhandling beskriver effekten av dubbelbrytning i is, vilket delar upp radiopulsen i två ortogonala polarisationskomponenter med något annorlunda propageringshastigheter. De signaturer som uppstår av dubbelbrytning kan hjälpa till att rekonstruera energin och riktningen hos neutrinon. I denna avhandling härleds effekterna av dubbelbrytning från grunden, där den enda fria parametern i modellen är den dielektriska tensorn som funktion av djup och riktning. Modellen som introduceras kan propagera fullständiga RF-vågformer, vilket för första gången möjliggör hänsynstagandet av interferensen som orsakas av förändrade polarisationsegenvektorer som uppstår under propageringen. Modellen är tillgänglig som öppen källkod via NuRadioMC-ramverket. Modellens förutsägelser jämförs med in-situ kalibreringsdata från experimenten ARA och ARIANNA, och vilka implikationer som modellen har för neutrinodetektion diskuteras.

High birefringence (Δn > 0.4) nematic liquid crystals are particularly attractive for infrared applications because they enable a thinner cell gap to be used for achieving fast response time and improved diffraction efficiency. In this thesis, the mesomorphic and electro‐optic properties of several new fluorinated isothiocyanate (NCS) terphenyl and phenyl tolane single compounds and mixtures are reported. The single compounds demonstrated Δn~0.35‐0.52 in the visible spectral region at room temperature and exhibit relatively low viscosity. It was found that lateral fluorine substitutions and short alkyl chains eliminate smectic phase and lower the melting temperature of the single compounds. However, the consequence of using highly conjugated compounds to improve electro‐optic properties is that the nematic phase is exhibited at high temperatures, over 100°C, and therefore single compounds cannot be used for device applications. Therefore, several mixtures based on the terphenyl and phenyl‐tolane compounds were formulated and evaluated. The purpose of mixtures is to find the optimum balance between electro‐optic performance and the mesomorphic properties that determine the operating temperature range. It was found that mixture formulations greatly improved mesomorphic properties to produce nematic phase at or near room temperature and suppressed smectic phase to below 0°C or eliminating completely. The analysis presented evaluates the benefits of lowering the operating temperature versus the consequence of degrading the electro‐optic properties.

Fiber analysis using birefringence has been around for years but has only recently been looked at more closely under a microscope. Recent scientists have proposed methods to correct issues found with fiber analysis using birefringence, yet there has not be a defined perfect method. This research will focus on correcting previously found issues with works by Michel-Lévy and Sorensen's, as well as other scientists involved and perfecting the analysis of fiber through birefringence. The goal will be to take this research one step further into the analysis of textile fibers by RGB value analysis and birefringence. The RGB values will be analyzed in a color analysis program to compare HEX values. The cross section of the fiber will be done to receive an accurate diameter measurement of the fiber. Those RGB values and cross section diameter will then be matched to the Michel-Lévy chart and the birefringence will be determined.

No description available.

No description available.

No description available.