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Polymer matrices doped with a dispersion of noble metal nanoparticles combine the strong plasmon resonance-based optical signatures of the latter with the flexibility and processability of the former. We have developed a nonlinear lithographic technique to generate large populations of epoxide waveguides containing a uniform dispersion of Au nanoparticles. The method is based on the self-trapping of multiple beams of white light propagating through a catonic polymerizable matrix doped with a gold salt, initiating the polymerization of epoxide moieties and simultaneously the in situ synthesis of elemental Au nanoparticles. Each white light filament inscribes a cylindrical waveguide, leading to an array of metallodielectric waveguides. Field of view (FOV) measurements indicate that the metallodielectric waveguide array has a nearly 59 % increase in FOV relative to its all-dielectric counterparts and can be tuned through the concentration of Au nanoparticles and the optical intensities employed to generate waveguides. / Thesis / Master of Science (MSc)

The nonlinear propagation of a visible, continuous wave laser beam was studied in three types of polymer systems that harness photochemical reactions: (i) a photopolymerization to create permanent self-written structures, (ii) a photo-oxidation hosted within a polymer matrix and (iii) a reversible photoisomerization that triggers the contraction of a photoresponsive hydrogel. The process of self-trapping was characterized by monitoring the spatial intensity profiles over time. The mechanism of each material was determined with a series of control experiments in order to confirm the nature of the nonlinear response, including their reversibility and intensity-dependence. These observations led to the study of interactions between self-trapped beams. Two beams under linear conditions will pass through one another, but two beams travelling in a nonlinear medium will interact and influence one another. The interactions of two beams introduced into the aforementioned photochemical systems were investigated and revealed a rich diversity of phenomena including: (i) the attraction between beams, (ii) merging of beams into a single waveguide, (iii) nonlocal attraction between beams, (iv) orbiting of beams, (v) switching of beam positions, and (vi) inhibition of the self-trapping of a neighbouring beam. Each observation is dependent on a detailed understanding of the underlying mechanism of refractive index change. Numerical simulations supplement some of these experiments and provide further evidence for the nonlinear mechanisms. The formation of permanent self-written structures with these nonlinear waves offers the opportunity to create seamless 3D printed materials with prismatic geometries. Several macroscopic objects were constructed using nonlinear waves from incoherent LEDs and amplitude masks. Decomposition of 3D objects into prismatic elements was carried out using an algorithm that breaks an object into individual pieces. Using a multi-step printing process, several prismatic elements can be combined to form a target object. The results of these experimental and theoretical studies improve upon the current understanding of the dynamics of nonlinear light propagation in photochemical systems. These insights may allow us to harness other nonlinear effects and develop new materials for applications such as optical communication, computing and 3D printing. / Thesis / Doctor of Science (PhD) / The nonlinear propagation of a visible, continuous wave laser beam was studied in three types of polymer systems that harness photochemical reactions: (i) a photopolymerization to create permanent self-written structures, (ii) a photo-oxidation hosted within a polymer matrix and (iii) a reversible photoisomerization that triggers the contraction of a photoresponsive hydrogel. Photochemical changes to the material lead to self-induced light-guiding structures that influence the behaviour of light. These self-trapped beams can interact with one another inside of a nonlinear medium, giving rise to a rich diversity of phenomena including: (i) the attraction between beams, (ii) merging of beams into a single waveguide, (iii) nonlocal attraction between beams, (iv) orbiting of beams, (v) switching of beam positions, and (vi) inhibition of the self-trapping of a neighbouring beam. Each observation is dependent on a detailed understanding of the underlying mechanism of refractive index change. Numerical simulations supplement some of these experiments and provide further evidence for the nonlinear mechanisms. The formation of permanent self-written structures with these nonlinear waves offers the opportunity to create seamless 3D printed materials with prismatic geometries. Several macroscopic objects were constructed using nonlinear waves from incoherent LEDs and amplitude masks. Decomposition of 3D objects into prismatic elements was carried out using an algorithm that breaks an object into individual pieces. Using a multi-step printing process, several prismatic elements can be combined to form a target object. The results of these experimental and theoretical studies improve upon the current understanding of the dynamics of nonlinear light propagation in photochemical systems. These insights may allow us to harness other nonlinear effects and develop new materials for applications such as optical communication, computing and 3D printing.

Effectiveness of a capture and return system for the partial retention of fermentation volatiles, as a means of improving white wine quality, was evaluated. Twenty-three aroma-active volatiles including ethyl esters, acetate esters, fusel alcohols, and fatty acids, were quantified using head-space solid phase microextraction with GC/MS. Volatile analysis of fermentations maintained at 15ºC demonstrated a trend of increased concentrations of ethanol, esters and ethyl esters of fatty acids and decreased concentrations of fusel alcohol acetates, fatty acids and higher alcohols in treatment wines. When fermentation temperature was maintained at 15ºC there was increased concentration and retention of fusel alcohols, fatty acids and higher alcohols compared to 15ºC. Sensory analysis of wines fermented at 15°C, using triangle difference testing, indicated variable differences in aroma among treatments. / Master of Science

Current research has shown that photophoretic optical trapping (POT) is a promising method for creating true three-dimensional holograms. A landmark study by Smalley et. al. at BYU was able to generate a full hologram within a 2 cm edge cube with remarkable success. However, a key drawback to this method is its poor ability to hold trapped particles within the focal point of the laser for an extended period of time. An investigation from our group presented at SPIE Photonics West 2023 sought to improve these results by varying the focal length of the trapping and the wavelength of the laser, called the one-lens control. To further extend trapping times, we take advantage of optical power lost due to scattering by reflecting it back toward the trapping site. We investigate the potential of retro-reflectors as an effective low-cost solution due to their corner- cube micro-structures which prevent interference between reflected and incident light. The reflected light is then re-focused back toward the trapping site using a Keplerian lens configuration. The resulting trapping times with retro-reflectors are measured and compared against two different control setups without reflectors, as well as a mirror setup to quantify the effects of destructive interference. Both the average and median trapping times for the retro-reflector setup showed significant improvement when compared to all three other test setups. While maximum trapping times with the retro-reflectors were comparable to those of the two-lens control setup, the new setup has higher average trapping times and shows great promise for future research. In addition we showed that at high optical laser powers the retro-reflectors showed higher average trapping times compared to the basic setup.

Ultrasonic wave propagation through a two-dimensional nonreciprocal phononic crystal with asymmetric aluminum rods in viscous water is studied for its application in Anderson localization and trapping of acoustic energy. A one-dimensional disorder in the otherwise 2D periodic crystal is introduced by disorienting the asymmetric rods along the rows and by keeping them equally oriented along the columns. An exponential decay of sound waves travelling along the direction of disorder is observed demonstrating Anderson localization whereas sound propagates as extended wave along the ordered direction. Localization length for the case of strong disorder with high randomness in the orientation of rods and weak disorder with weak fluctuations in the orientation of rods is evaluated. The degree of randomness in the orientation of the rods controls the localization length of the wave. Thouless's theoretical prediction for the scaling of Lyapunov exponent with disorder is experimentally observed for weak disorder at frequency in the transmission band and anomalous scaling is observed for band edge frequency. Transmission spectra of acoustic waves is also measured for opposite direction of propagation and nonreciprocity is observed for the exponentially weak transmission in the disordered direction as well as for extended states in the ordered direction. Breaking of reciprocity in the current structure is due to the broken PT symmetry. The T symmetry or the time reversal symmetry is broken by the viscous dissipation at the boundaries of scatterers and the water, and the P symmetry is broken by the asymmetric shape of the rods. Acoustic energy trapping inside a nonreciprocal phononic crystal cavity is studied by creating three configurations of cavities. These configurations are based on the orientation of the asymmetric scatterers on each side of the cavity. Only one of these configuration utilizes the nonreciprocal property of the structure. Enhancement of energy trapping in the cavity is observed for the cavity orientation utilizing nonreciprocity. The proposed enhancement of energy trapping occurs at the transmission band frequency unlike the extensively used mechanism of energy trapping at the defect modes of the band gap of the phononic crystal. All the experimental results are verified numerically using finite element based modelling in COMSOL Multiphysics. The proposed devices can be utilized for applications in one way sound transmission, noise control, isolators, circulators and energy harvesting.

Le but de cette thèse consistait en l’amélioration de l’activité thérapeutique d’agents anti-radicalaires synthétiques de type nitroxyde et nitrone. Ces deux classes d’antioxydants synthétiques ont été choisies pour leur très bonne activité de piégeurs de radicaux libres, des substances particulièrement délétères et impliquées à l’heure actuelle dans un grand nombre de pathologies. Dans une première partie de ce travail, des nitroxydes ont été fonctionnalisés par des transporteurs amphiphiles dérivés de la lysine et de l’acide aspartique, puis une deuxième approche a consisté en la modification d’une nitrone, l’alphaphényl-N-tert-butyl-nitrone (PBN) par des groupements polaires et apolaires. Les études physico-chimiques ont ensuite permit de caractériser les propriétés d’auto-assemblage en milieux aqueux de ces composés ainsi que leur caractère hydrophobe et leurs propriétés antioxydantes. Enfin, des études biologiques ont mis en évidence les propriétés protectrices de ces molécules vis-à-vis des phénomènes de stress oxydant sur des modèles in vitro et in vivo. / The goal of this thesis was to improve the therapeutic activity of synthetic nitroxide and nitrone antioxidant agents. Free radicals are very reactive and toxic species that are associated to a large number of pathologies. In the first part of this work, nitroxides were grafted to lysine- and aspartic acid- based amphiphilic carriers. The second part, consisted inthe functionalization of the α-phenyl-N-tert-butyl-nitrone (PBN) by hydrophilic and lipophilic groups. For both series of compounds the self-aggregation properties in water as well as their hydrophobic character and antioxidant properties were determined. Finally, biological studies demonstrated the protective properties of these molecules against oxidative stress in vitro and in vivo models.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2006. / Title from title page screen (viewed on Jan. 31, 2007). Thesis advisor: Lisa I. Muller. Vita. Includes bibliographical references.

Die heutige optische Informationsverarbeitung erfordert neue Materialien, die Licht effektiv verarbeiten, steuern und speichern können. Photorefraktive (PR) Materialien sind dafür sehr interessant. In diesen Materialien entsteht bei inhomogener Beleuchtung (z.B. mit einem Intererenzmuster) über Ladungsträgergenerierung und Einfang der Ladungsträger in Fallen ein Raumladungsfeld. Dieses wird über den elektrooptischen Effekt in eine räumliche Modulation des Brechungsindex umgesetzt. Letztendlich führt somit die inhomogene Beleuchtung eines PR-Materials zu einer räumlich variierenden Änderung des Brechungsindex. Vor ca. 10 Jahren wurde entdeckt, dass auch Polymere einen PR-Effekt aufweisen können. Die Ansprechzeit dieser Materialien wird dabei wesentlich durch die Dynamik der Ladungsträger (bestimmt durch Erzeugung, Transport, Einfang in Fallen etc.) begrenzt. Bis zu Beginn dieser Arbeit war es noch nicht gelungen, einen quantitativen Zusammenhang zwischen der Ladungsträgerdynamik und der Ansprechzeit des PR-Effekts experimentell nachzuweisen. In dieser Arbeit wird ein Weg aufgezeigt, durch photophysikalische Experimente unter verschiedenen Beleuchtungsbedingungen alle photophysikalischen Größen experimentell zu bestimmen, die den Aufbau des Raumladungsfelds in organischen photorefraktiven Materialien bestimmen. So konnte durch Experimente unter Beleuchtung mit kurzen Einzelpulsen sowohl die Beweglichkeit der freien Ladungsträger als auch die charakteristischen Parameter flacher Fallen ermittelt werden. Zur Bestimmung der Dichte tiefer Fallen wurde die Intensitätsabhängigkeit des stationären Photostroms untersucht. Durch die analytische Lösung des bestimmenden Gleichungssystems konnte gezeigt werden, dass die Sublinearität der Intensitätsabhängigkeit des Photostroms primär mit dem Verhältnis zwischen Entleerungs- und Einfangkoeffizienten tiefer Fallen korreliert. Zur unabhängigen Bestimmung des Entleerungskoeffizienten der tiefen Fallen wurden Doppelpulsexperimente mit variabler Verzögerungszeit zwischen den Pulsen verwendet. Mit den erhaltenen Parametern konnte dann das untere Limit der zum Aufbau des Raumladungsfelds notwendigen Zeit abgeschätzt werden. Diese Werte wurden mit den gemessenen photorefraktiven Ansprechzeiten verglichen. Es zeigt sich, dass weder die Photogeneration noch der Transport der Ladungsträger die Geschwindigkeit des Aufbaus des Raumladungsfeldes limitiert. Stattdessen konnte erstmals quantitativ nachgewiesen werden, dass die Dynamik des Raumladungsfelds in den hier untersuchten PR-Materialien durch das Füllen tiefer Fallen mit photogenerierten Ladungsträgern bestimmt wird. Dabei spielt das Verhältnis zwischen dem Einfang- und dem Rekombinationskoeffizienten eine wesentliche Rolle. Weiterhin wurde die Dynamik des Aufbaus des Raumladungsfelds bei unterschiedlichen Vorbeleuchtungsbedingungen quantitativ simuliert und mit den experimentellen PR-Transienten verglichen. Die gute Übereinstimmung zwischen den simulierten und gemessenen Transienten erlaubte es abschließend, die kritischen Parameter, die die Dynamik des PR-Effekts in den untersuchten Polymeren begrenzen, zu identifizieren. / The ongoing development of information processing requires new materials that are capable of effective light modulation, processing or storage. Photorefractive (PR) materials characterized by a reversible light-induced change of the refractive index have been effectively used for different optical applications. When a photorefractive medium is inhomogeneously irradiated, using for example an interference pattern, the generation, transport and trapping of the charge carriers results in the formation of a space charge field. The spatial modulation of the space charge field is transformed through the electro-optical effect into a modulation of the refractive index.<br /> While photorefractive crystals are well known since the discovery of the PR effect in 1966, the photorefractive effect in polymers has only recently been demonstrated. The flexibility of material composition and thus its parameters along with easy processability of polymer materials essentially extends the range of possible applications of photorefractive materials. The response time of PR polymers is defined by the charge carrier dynamics including generation, transport, trapping etc. But a relation between the charge carriers dynamics and the response time of PR effect has not yet been proven experimentally. In this work a method for the experimental determination of all photo-physical parameters defining the formation of the space charge field in organic photorefractive materials has been proposed for the first time. It is based on the analysis of the photocurrent measured under different irradiation conditions such as continuous and pulse irradiation with different intensities, the variation of the pulse length, the number of pulses or the delay between pulses. Thus, the irradiation with single short pulses allowed to determine the mobility of free charge carriers as well as the characteristic parameters of shallow traps. In order to determine the density of deep traps, the intensity dependence of the steady-state photocurrent was investigated. The determining system of equations was analytically solved and it has been shown that the sublinear dependence of the photocurrent on intensity is primary correlated with the ratio of detrapping and trapping coefficients for deep traps. The detrapping coefficient of deep traps was independently determined from double-pulse experiments in which the delay between two pulses was varied. The dynamics of the space charge field formation has been numerically simulated, using the obtained photophysical parameters, and proven to coincide well with the experimentally determined dynamics of the PR effect. This allowed to relate the parameters of the individual processes participating in the formation of the space charge field to the dynamics of the PR effect in the investigated polymers. These results show that neither photogeneration nor transport of the charge carriers do limit the formation of the space charge field. It is demonstrated that in the investigated PR materials the dynamics of the space charge field is limited by the filling of deep traps with the photogenerated charge carriers.