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Articles 160561 - 160590 of 293715

Full-Text Articles in Physical Sciences and Mathematics

High Flux Isolated Attosecond Pulse Generation, Yi Wu Jan 2013

High Flux Isolated Attosecond Pulse Generation, Yi Wu

Electronic Theses and Dissertations

This thesis outlines the high intensity tabletop attosecond extreme ultraviolet laser source at the Institute for the Frontier of Attosecond Science and Technology Laboratory. First, a unique Ti:Sapphire chirped pulse amplifier laser system that delivers 14 fs pulses with 300 mJ energy at a 10 Hz repetition rate was designed and built. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two stage Ti:Sapphire chirped pulse power amplifier with mJ-level white light pulses from a gas filled hollow core fiber. It is the highest energy level ever achieved by a broadband pulse in a …

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Enhanced Two-Photon Absorption In A Squaraine-Fluorene-Squaraine Dye: Design, Synthesis, Photophysical Properties, And Solvatochromic Behavior, William Moreshead Jan 2013

Enhanced Two-Photon Absorption In A Squaraine-Fluorene-Squaraine Dye: Design, Synthesis, Photophysical Properties, And Solvatochromic Behavior, William Moreshead

Electronic Theses and Dissertations

The discovery of any new technology is usually accompanied by a need for new or improved materials which make that technology useful in practical applications. In the case of two-photon absorption (2PA) this has truly been the case. Since its first demonstration in 1961, there has been an ever increasing quest to understand the relationships between two-photon absorption and the structure of two-photon absorbing materials. This quest has been motivated by the many applications for 2PA which have been reported, including fluorescence bioimaging, 3D microfabrication, 3D optical data storage, upconverted lasing, and photodynamic therapy. The work presented in this dissertation …

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Development Of Micro Volume Dna And Rna Profiling Assays To Identify The Donor And Tissue Source Of Origin Of Trace Forensic Biological Evidence, Brittany Morgan Jan 2013

Development Of Micro Volume Dna And Rna Profiling Assays To Identify The Donor And Tissue Source Of Origin Of Trace Forensic Biological Evidence, Brittany Morgan

Electronic Theses and Dissertations

In forensic casework analysis it is necessary to obtain genetic profiles from increasingly smaller amounts of biological material left behind by perpetrators of crime. The ability to obtain profiles from trace biological evidence is demonstrated with so-called ‘touch DNA evidence’ which is perceived to be the result of DNA obtained from shed skin cells transferred from donor to an object or person during physical contact. However, the current method of recovery of trace DNA involves cotton swabs or adhesive tape to sample an area of interest. This "blindswabbing" approach may result in the recovery of biological material from different individuals …

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Squaraine Dyes, Design And Synthesis For Various Functional Materials Applications, Yuanwei Zhang Jan 2013

Squaraine Dyes, Design And Synthesis For Various Functional Materials Applications, Yuanwei Zhang

Electronic Theses and Dissertations

This dissertation contains the synthesis and characterization of squaraine based new functional materials. In the first part of this thesis work, a water soluble benzothiazolium squaraine dye was synthesized with pyridium pendents, and controlled aggregation properties were achieved. After formation of partially reversible J-aggregation on a polyelectrolyte (poly(acryl acid) sodium salt) template, the nonlinear, two-photon absorption cross section per repeat unit was found to be above 30-fold enhanced compared with nonaggregate and/or low aggregates. Using a similar strategy, sulfonate anions were introduced into the squaraine structure, and the resulting compounds exhibited good water solubilities. A ‘turn on’ fluorescence was discovered …

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Optically Induced Forces In Scanning Probe Microscopy, Dana Kohlgraf-Owens Jan 2013

Optically Induced Forces In Scanning Probe Microscopy, Dana Kohlgraf-Owens

Electronic Theses and Dissertations

The focus of this dissertation is the study of measuring light not by energy transfer as is done with a standard photodetector such as a photographic film or charged coupled device, but rather by the forces which the light exerts on matter. In this manner we are able to replace or complement standard photodetector-based light detection techniques. One key attribute of force detection is that it permits the measurement of light over a very large range of frequencies including those which are difficult to access with standard photodetectors, such as the far IR and THz. The dissertation addresses the specific …

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Partially Integrable Pt-Symmetric Hierarchies Of Some Canonical Nonlinear Partial Differential Equations, Keri Pecora Jan 2013

Partially Integrable Pt-Symmetric Hierarchies Of Some Canonical Nonlinear Partial Differential Equations, Keri Pecora

Electronic Theses and Dissertations

In this dissertation, we generalize the work of Bender and co-workers to derive new partially-integrable hierarchies of various PT -symmetric, nonlinear partial differential equations. The possible integrable members are identified employing the Painlev´e Test, a necessary but not sufficient integrability condition, and are indexed by the integer n, corresponding to the negative of the order of the dominant pole in the singular part of the Painlev´e expansion for the solution. For the PT -symmetric Korteweg-de Vries (KdV) equation, as with some other hierarchies, the first or n = 1 equation fails the test, the n = 2 member corresponds to …

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Novel Optical Properties Of Metal Nanostructures Based On Surface Plasmons, Haining Wang Jan 2013

Novel Optical Properties Of Metal Nanostructures Based On Surface Plasmons, Haining Wang

Electronic Theses and Dissertations

Surface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal nanostructures. With a perforated silver film, we demonstrated that an extremely low scattering cross section with an efficiency of less than 1% can be achieved at tunable wavelengths with tunable widths. …

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Numerical Simulations For The Flow Of Rocket Exhaust Through A Granular Medium, Kristina Kraakmo Jan 2013

Numerical Simulations For The Flow Of Rocket Exhaust Through A Granular Medium, Kristina Kraakmo

Electronic Theses and Dissertations

Physical lab experiments have shown that the pressure caused by an impinging jet on a granular bed has the potential to form craters. This poses a danger to landing success and nearby spacecraft for future rocket missions. Current numerical simulations for this process do not accurately reproduce experimental results. Our goal is to produce improved simulations to more accurately and effi- ciently model the changes in pressure as gas flows through a porous medium. A two-dimensional model in space known as the nonlinear Porous Medium Equation as it is derived from Darcy’s law is used. An Alternating-Direction Implicit (ADI) temporal …

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Engineering And Application Of Ultrafast Laser Pulses And Filamentation In Air, Nicholas Barbieri Jan 2013

Engineering And Application Of Ultrafast Laser Pulses And Filamentation In Air, Nicholas Barbieri

Electronic Theses and Dissertations

Continuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter. The need to better control the light obtained from increasingly advanced laser sources leads to the emergence of beam engineering, the systematic understanding and control of light through refractive media and …

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Ytterbium-Doped Fiber-Seeded Thin-Disk Master Oscillator Power Amplifier Laser System, Christina Willis-Ott Jan 2013

Ytterbium-Doped Fiber-Seeded Thin-Disk Master Oscillator Power Amplifier Laser System, Christina Willis-Ott

Electronic Theses and Dissertations

Lasers which operate at both high average power and energy are in demand for a wide range of applications such as materials processing, directed energy and EUV generation. Presented in this dissertation is a high-power 1 μm ytterbium-based hybrid laser system with temporally tailored pulse shaping capability and up to 62 mJ pulses, with the expectation the system can scale to higher pulse energies. This hybrid system consists of a low power fiber seed and pre-amplifier, and a solid state thin-disk regenerative amplifier. This system has been designed to generate high power temporally tailored pulses on the nanosecond time scale. …

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High Energy, High Average Power, Picosecond Laser Systems To Drive Few-Cycle Opcpa, Andreas Vaupel Jan 2013

High Energy, High Average Power, Picosecond Laser Systems To Drive Few-Cycle Opcpa, Andreas Vaupel

Electronic Theses and Dissertations

The invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA allows direct amplification of an almost-octave spanning bandwidth supporting few-cycle pulse durations at center wavelengths ranging from the visible to the mid-IR. The current record in peak power from a …

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Pulsed Tm-Fiber Laser For Mid-Ir Generation, Pankaj Kadwani Jan 2013

Pulsed Tm-Fiber Laser For Mid-Ir Generation, Pankaj Kadwani

Electronic Theses and Dissertations

The thulium fiber laser has gained interest due to its long emission wavelength, large bandwidth (~1.8 – 2.1 µm), high efficiencies (~60 %), and high output power levels both in cw as well as pulsed regimes. Applications like remote sensing, machining, medical tissue ablation, and mid-infrared generation benefit from high peak power thulium laser sources. Pulsed thulium fiber laser systems are advancing rapidly towards higher peak power levels and are becoming the preferred sources for these applications. This dissertation work describes the development of novel nanosecond pulsed thulium fiber laser systems with record high peak power levels targeting mid-infrared generation. …

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Fast-Response Liquid Crystals For Photonic And Display Applications, Jie Sun Jan 2013

Fast-Response Liquid Crystals For Photonic And Display Applications, Jie Sun

Electronic Theses and Dissertations

Liquid crystal devices are attractive for many applications such as information displays, spatial light modulators and adaptive optics, because their optical properties are electrically tunable. However, response time of liquid crystal devices is a serious concern for many applications especially for those who require large phase modulation (≥2π). This is because a thick LC layer is usually needed to achieve a large phase shift while the response time of a nematic LC is highly determined by the cell gap.

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An Exploration Of Unmanned Aerial Vehicle Direct Manipulation Through 3d Spatial Interaction, Kevin Pfeil Jan 2013

An Exploration Of Unmanned Aerial Vehicle Direct Manipulation Through 3d Spatial Interaction, Kevin Pfeil

Electronic Theses and Dissertations

We present an exploration that surveys the strengths and weaknesses of various 3D spatial interaction techniques, in the context of directly manipulating an Unmanned Aerial Vehicle (UAV). Particularly, a study of touch- and device- free interfaces in this domain is provided. 3D spatial interaction can be achieved using hand-held motion control devices such as the Nintendo Wiimote, but computer vision systems offer a different and perhaps more natural method. In general, 3D user interfaces (3DUI) enable a user to interact with a system on a more robust and potentially more meaningful scale. We discuss the design and development of various …

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Smooth And Non-Smooth Traveling Wave Solutions Of Some Generalized Camassa-Holm Equations, Taslima Rehman Jan 2013

Smooth And Non-Smooth Traveling Wave Solutions Of Some Generalized Camassa-Holm Equations, Taslima Rehman

Electronic Theses and Dissertations

In this thesis we employ two recent analytical approaches to investigate the possible classes of traveling wave solutions of some members of recently derived integrable family of generalized Camassa-Holm (GCH) equations. In the first part, a novel application of phase-plane analysis is employed to analyze the singular traveling wave equations of four GCH equations, i.e. the possible non-smooth peakon, cuspon and compacton solutions. Two of the GCH equations do no support singular traveling waves. We generalize an existing theorem to establish the existence of peakon solutions of the third GCH equation. This equation is found to also support four segmented, …

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Wavelength Scale Resonant Structures For Integrated Photonic Applications, Matthew Weed Jan 2013

Wavelength Scale Resonant Structures For Integrated Photonic Applications, Matthew Weed

Electronic Theses and Dissertations

An approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled cavity systems offer the designer slow light propagation which increases photon lifetime, reduces size limitations toward on-chip integration, and offers enhanced light-matter interaction. A unique resonant structure explained by various numerical models …

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Active Learning With Unreliable Annotations, Liyue Zhao Jan 2013

Active Learning With Unreliable Annotations, Liyue Zhao

Electronic Theses and Dissertations

With the proliferation of social media, gathering data has became cheaper and easier than before. However, this data can not be used for supervised machine learning without labels. Asking experts to annotate sufficient data for training is both expensive and time-consuming. Current techniques provide two solutions to reducing the cost and providing sufficient labels: crowdsourcing and active learning. Crowdsourcing, which outsources tasks to a distributed group of people, can be used to provide a large quantity of labels but controlling the quality of labels is hard. Active learning, which requires experts to annotate a subset of the most informative or …

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The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell Jan 2013

The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell

Electronic Theses and Dissertations

Cubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated. Plasma-Enhanced Molecular Beam Epitaxy was used to grow Zn1-xMgxO thin films and formation conditions were explored by varying the growth temperature, Mg source flux, oxygen flow rate, and radio-frequency (RF) power coupled into …

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Spectrally Uniform Frames And Spectrally Optimal Dual Frames, Saliha Pehlivan Jan 2013

Spectrally Uniform Frames And Spectrally Optimal Dual Frames, Saliha Pehlivan

Electronic Theses and Dissertations

Frames have been useful in signal transmission due to the built in redundancy. In recent years, the erasure problem in data transmission has been the focus of considerable research in the case the error estimate is measured by operator (or matrix) norm. Sample results include the characterization of one-erasure optimal Parseval frames, the connection between two-erasure optimal Parseval frames and equiangular frames, and some characterization of optimal dual frames. If iterations are allowed in the reconstruction process of the signal vector, then spectral radius measurement for the error operators is more appropriate then the operator norm measurement. We obtain a …

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Prediction Of Optical Properties Of Pi-Conjugated Organic Materials For Technological Innovations, Iffat Nayyar Jan 2013

Prediction Of Optical Properties Of Pi-Conjugated Organic Materials For Technological Innovations, Iffat Nayyar

Electronic Theses and Dissertations

Organic π-conjugated solids are promising candidates for new optoelectronic materials. The large body of evidence points at their advantageous properties such as high charge-carrier mobility, large nonlinear polarizability, mechanical flexibility, simple and low cost fabrication and superior luminescence. They can be used as nonlinear optical (NLO) materials with large two-photon absorption (2PA) and as electronic components capable of generating nonlinear neutral (excitonic) and charged (polaronic) excitations. In this work, we investigate the appropriate theoretical methods used for the (a) prediction of 2PA properties for rational design of organic materials with improved NLO properties, and (b) understanding of the essential electronic …

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Modified Pal Interpolation And Sampling Bilevel Signals With Finite Rate Of Innovation, Gayatri Ramesh Jan 2013

Modified Pal Interpolation And Sampling Bilevel Signals With Finite Rate Of Innovation, Gayatri Ramesh

Electronic Theses and Dissertations

Sampling and interpolation are two important topics in signal processing. Signal processing is a vast field of study that deals with analysis and operations of signals such as sounds, images, sensor data, telecommunications and so on. It also utilizes many mathematical theories such as approximation theory, analysis and wavelets. This dissertation is divided into two chapters: Modified Pal´ Interpolation and Sampling Bilevel Signals with Finite Rate of Innovation. In the first chapter, we introduce a new interpolation process, the modified Pal interpolation, based on papers by P ´ al, J ´ oo´ and Szabo, and we establish the existence and …

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Light-Matter Interactions Of Plasmonic Nanostructures, Jennifer Reed Jan 2013

Light-Matter Interactions Of Plasmonic Nanostructures, Jennifer Reed

Electronic Theses and Dissertations

Light interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective oscillation of the conduction electrons in the metal. Since the conduction electrons can be thought of as harmonic oscillators, they are quantized in a similar fashion. Just …

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Theoretical And Computational Studies Of Diffusion Of Adatom Islands And Reactions Of Molecules On Surfaces, Syed Islamuddin Shah Jan 2013

Theoretical And Computational Studies Of Diffusion Of Adatom Islands And Reactions Of Molecules On Surfaces, Syed Islamuddin Shah

Electronic Theses and Dissertations

The work presented in this dissertation focuses on the study of post deposition spatial and temporal evolution of adatom islands and molecules on surfaces using ab initio and semiemperical methods. It is a microscopic study of the phenomena of diffusion and reaction on nanostructured surfaces for which we have developed appropriate computational tools, as well as implemented others that are available. To map out the potential energy surface on which the adatom islands and molecules move, we have carried out ab initio electronic structure calculations based on density functional theory (DFT) for selected systems. For others, we have relied on …

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Growth And Characterization Of Zno Based Semiconductor Materials And Devices, Ming Wei Jan 2013

Growth And Characterization Of Zno Based Semiconductor Materials And Devices, Ming Wei

Electronic Theses and Dissertations

Wide band gap semiconductors such as MgxZn1-xO represent an excellent choice for making optical photodetectors and emitters operating in the UV spectral region. High crystal and optical quality MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and sub-nanometer surface roughness were achieved by applying a low temperature nucleation layer. The critical growth conditions were discussed to obtain a high quality film: the sequence of Zn and O sources for initial growth of nucleation layer, growth temperatures for both ZnO nucleation and …

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Optically Isotropic Liquid Crystals For Display And Photonic Applications, Jin Yan Jan 2013

Optically Isotropic Liquid Crystals For Display And Photonic Applications, Jin Yan

Electronic Theses and Dissertations

For the past few decades, tremendous progress has been made on liquid crystal display (LCD) technologies in terms of stability, resolution, contrast ratio, and viewing angle. The remaining challenge is response time. The state-of-the-art response time of a nematic liquid crystal is a few milliseconds. Faster response time is desirable in order to reduce motion blur and to realize color sequential display using RGB LEDs, which triples the optical efficiency and resolution density. Polymer-stabilized blue phase liquid crystal (PS-BPLC) is a strong candidate for achieving fast response time because its self-assembled cubic structure greatly reduces the coherence length. The response …

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Inverse Problems In Multiple Light Scattering, John Broky Jan 2013

Inverse Problems In Multiple Light Scattering, John Broky

Electronic Theses and Dissertations

The interaction between coherent waves and material systems with complex optical properties is a complicated, deterministic process. Light that scatters from such media gives rise to random fields with intricate properties. It is common perception that the randomness of these complex fields is undesired and therefore is to be removed, usually through a process of ensemble averaging. However, random fields emerging from light matter interaction contain information about the properties of the medium and a thorough analysis of the scattered light allows solving specific inverse problems. Traditional attempts to solve these kinds of inverse problems tend to rely on statistical …

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Mechanochemistry For Solid-State Syntheses And Catalysis, David Restrepo Jan 2013

Mechanochemistry For Solid-State Syntheses And Catalysis, David Restrepo

Electronic Theses and Dissertations

Traditional methods of synthesizing inorganic materials, such as hydrothermal, sol-gel, calcination and grinding steps, can typically require use of high temperatures, expensive precursors or use of solvents. Because of the energy-intensive nature or environmental impact these techniques, there is a push, especially from an industrial perspective, to move towards greener approaches. Mechanochemistry is a solvent-free alternative technique that can be used to synthesize a variety of materials under ambient conditions. Due to this, there is an increase in attention towards the use of this approach in both solid-state inorganic and organic chemistry. This dissertation reports the mechanochemical synthesis of a …

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Similarity Of Climate Control On Base Flow And Perennial Stream Density In The Budyko Framework, Liuliu Wu Jan 2013

Similarity Of Climate Control On Base Flow And Perennial Stream Density In The Budyko Framework, Liuliu Wu

Electronic Theses and Dissertations

Streams are classified into perennial, intermittent, and ephemeral streams based on flow durations. Perennial stream is the basic network, while intermittent or ephemeral stream is the expanded network. Connection between perennial stream and base flow at the mean annual scale exists since one of the hydrologic functions of perennial stream is to deliver runoff even in low flow seasons. The partitioning of precipitation into runoff and evaporation at the mean annual scale, on the first order, is captured by the ratio of potential evaporation to precipitation (Ep/P called climate aridity index) based on the Budyko hypothesis. The primary focus of …

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Theoretical Studies Of Nanostructure Formation And Transport On Surfaces, Maral Aminpour Jan 2013

Theoretical Studies Of Nanostructure Formation And Transport On Surfaces, Maral Aminpour

Electronic Theses and Dissertations

This dissertation undertakes theoretical and computational research to characterize and understand in detail atomic configurations and electronic structural properties of surfaces and interfaces at the nano-scale, with particular emphasis on identifying the factors that control atomic-scale diffusion and transport properties. The overarching goal is to outline, with examples, a predictive modeling procedure of stable structures of novel materials that, on the one hand, facilitates a better understanding of experimental results, and on the other hand, provide guidelines for future experimental work. The results of this dissertation are useful in future miniaturization of electronic devices, predicting and engineering functional novel nanostructures. …

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Planar Organic Photovoltaic Devices, Feras Alzubi Jan 2013

Planar Organic Photovoltaic Devices, Feras Alzubi

Electronic Theses and Dissertations

Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical …

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