Dynamical Theory Calculations Of Spin-Echo Resolved Grazing-Incidence Scattering From A Diffraction Grating,
2010
Indiana University - Bloomington
Dynamical Theory Calculations Of Spin-Echo Resolved Grazing-Incidence Scattering From A Diffraction Grating, Rana Ashkar, P. Stonaha, A. L. Washington, V. R. Shah, M. R. Fitzsimmons, B. Maranville, C. F. Majkrzak, W. T. Lee, W. L. Schaich, Roger Pynn
Nebraska Center for Materials and Nanoscience: Faculty Publications
Neutrons scattered or reflected from a diffraction grating are subject to a periodic potential analogous to the potential experienced by electrons within a crystal. Hence, the wavefunction of the neutrons can be expanded in terms of Bloch waves and a dynamical theory can be applied to interpret the scattering phenomenon. In this paper, a dynamical theory is used to calculate the results of neutron spin-echo resolved grazing-incidence scattering (SERGIS) from a silicon diffraction grating with a rectangular profile. The calculations are compared with SERGIS measurements made on the same grating at two neutron sources: a pulsed source and a continuous …
Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study,
2010
University of South Carolina - Columbia
Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden
Faculty Publications
The interaction of Aun and Ptn (n=2,3) clusters with the stoichiometric and partially reduced rutile TiO2 (110) surfaces has been investigated using periodic slab and periodic electrostatic embedded cluster models. Compared to Au clusters, Pt clusters interact strongly with both stoichiometric and reduced TiO2 (110) surfaces and are able to enhance the reducibility of the TiO2 (110) surface, i.e., reduce the oxygen vacancy formation energy. The focus of this study is the effect of Hartree–Fock exchange on the description of the strength of chemical bonds at the interface of Au/Pt clusters and the TiO2 (110) surface. Hartree–Fock exchange helps describing …
Surface Plasmon Hosts For Infrared Waveguides And Biosensors, And Plasmons In Gold-Black Nano-Structured Films,
2010
University of Central Florida
Surface Plasmon Hosts For Infrared Waveguides And Biosensors, And Plasmons In Gold-Black Nano-Structured Films, Justin Cleary
Electronic Theses and Dissertations
Applications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 µm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra and where the refractive index is increased by dispersion, which will provide enhanced selectivity and sensitivity. …
Freeform Reflector Design With Extended Sources,
2010
University of Central Florida
Freeform Reflector Design With Extended Sources, Florian Fournier
Electronic Theses and Dissertations
Reflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a desired target distribution with a reflective surface. Design methods for systems with rotational and translational symmetry were devised in the 1930s. …
Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications,
2010
University of Central Florida
Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim
Electronic Theses and Dissertations
In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Perot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved two-section device. …
Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures,
2010
University of Central Florida
Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel
Electronic Theses and Dissertations
The application of epitaxially grown, III-V semiconductor-based nanostructures to the development of electro-optical and all-optical switches is investigated through the fabrication and testing of integrated photonic devices designed using multimode interference (MMI) waveguides. The properties and limitations of the materials are explored with respect to the operation of those devices through electrical carrier injection and optical pumping. MMI waveguide geometry was employed as it offered advantages such as a very compact device footprint, low polarization sensitivity, large bandwidth and relaxed fabrication tolerances when compared with conventional single-mode waveguide formats. The first portion of this dissertation focuses on the characterization of …
Accelerating Optical Airy Beams,
2010
University of Central Florida
Accelerating Optical Airy Beams, Georgios Siviloglou
Electronic Theses and Dissertations
Over the years, non-spreading or non-diffracting wave configurations have been systematically investigated in optics. Perhaps the best known example of a diffraction-free optical wave is the so-called Bessel beam, first suggested and observed by Durnin et al. This work sparked considerable theoretical and experimental activity and paved the way toward the discovery of other interesting non-diffracting solutions. In 1979 Berry and Balazs made an important observation within the context of quantum mechanics: they theoretically demonstrated that the Schrodinger equation describing a free particle can exhibit a non-spreading Airy wavepacket solution. This work remained largely unnoticed in the literature-partly because such …
Misalignment Induced Nodal Aberration Fields And Their Use In The Alignment Of Astronomical Telescopes,
2010
University of Central Florida
Misalignment Induced Nodal Aberration Fields And Their Use In The Alignment Of Astronomical Telescopes, Tobias Schmid
Electronic Theses and Dissertations
Following the foundation of aberration theory for rotationally symmetric optical systems established by Seidel, Schwarzschild, Burch, Conrady, Buchdahl, and in its most useful form H.H. Hopkins, Shack, Buchroeder, Thompson, and Rogers developed a vectorial form of the wave aberration theory that enables addressing optical systems without symmetry. In this research, a vectorial theory is utilized and extended for the alignment of two- and three-mirror astronomical telescopes, including the effects of pointing changes and astigmatic figure errors. Importantly, it is demonstrated that the vectorial form of aberration theory, also referred to as nodal aberration theory, not only provides valuable insights but …
Near-Field Optical Interactions And Applications,
2010
University of Central Florida
Near-Field Optical Interactions And Applications, David Haefner
Electronic Theses and Dissertations
The propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is overcome only through a secondary interaction that couples the high-spatial-frequency (but non-propagating) field components to propagating waves that can be detected. The available information depends intrinsically on this secondary interaction, …
Structural, Electronic, Vibrational And Thermodynamical Properties Of Surfaces And Nanoparticles,
2010
University of Central Florida
Structural, Electronic, Vibrational And Thermodynamical Properties Of Surfaces And Nanoparticles, Handan Yildirim
Electronic Theses and Dissertations
The main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the 'bottom-up' approach for which the knowledge gathered at the scale of atoms and NPs serves as a base to build, at the macroscopic scale, materials with desired physical and chemical properties. We use a …
Epitaxial Growth, Characterization And Application Of Novel Wide Bandgap Oxide Semiconductors,
2010
University of Central Florida
Epitaxial Growth, Characterization And Application Of Novel Wide Bandgap Oxide Semiconductors, Jeremy Mares
Electronic Theses and Dissertations
In this work, a body of knowledge is presented which pertains to the growth, characterization and exploitation of high quality, novel II-IV oxide epitaxial films and structures grown by plasma-assisted molecular beam epitaxy. The two compounds of primary interest within this research are the ternary films NixMg1-xO and ZnxMg1-xO and the investigation focuses predominantly on the realization, assessment and implementation of these two oxides as optoelectronic materials. The functioning hypothesis for this largely experimental effort has been that these cubic ternary oxides can be exploited - and possibly even juxtaposed - to realize novel wide band gap optoelectronic technologies. The …
Micro-Electro-Mechanical Systems (Mems) And Agile Lensing-Based Modules For Communications, Sensing And Signal Processing.,
2010
University of Central Florida
Micro-Electro-Mechanical Systems (Mems) And Agile Lensing-Based Modules For Communications, Sensing And Signal Processing., Syed Reza
Electronic Theses and Dissertations
This dissertation proposes the use of the emerging Micro-Electro-Mechanical Systems (MEMS) and agile lensing optical device technologies to design novel and powerful signal conditioning and sensing modules for advanced applications in optical communications, physical parameter sensing and RF/optical signal processing. For example, these new module designs have experimentally demonstrated exceptional features such as stable loss broadband operations and high > 60 dB optical dynamic range signal filtering capabilities. The first part of the dissertation describes the design and demonstration of digital MEMS-based signal processing modules for communication systems and sensor networks using the TI DLP (Digital Light Processing) technology. Examples of …
Fast Response Dual Frequency Liquid Crystal Materials,
2010
University of Central Florida
Fast Response Dual Frequency Liquid Crystal Materials, Qiong Song
Electronic Theses and Dissertations
Dual frequency liquid crystal (DFLC) exhibits a positive dielectric anisotropy at low frequencies and negative dielectric anisotropy at high frequencies. The frequency where dielectric anisotropy is zero is called crossover frequency. DFLC can achieve fast rise time and fast decay time with the assistance of applied voltage. However, one drawback of DFLC is that it has dielectric heating effect when driven at a high frequency. Thus, the first part of this dissertation is to develop low crossover frequency DFLC materials. The dielectric relaxation and physical properties of some single- and double-ester compounds were investigated. Experimental results indicate that the double-ester …
Experimental And Theoretical Approaches To Characterization Of Electronic Nonlinearities In Direct-Gap Semiconductors,
2010
University of Central Florida
Experimental And Theoretical Approaches To Characterization Of Electronic Nonlinearities In Direct-Gap Semiconductors, Claudiu Cirloganu
Electronic Theses and Dissertations
The general goal of this dissertation is to provide a comprehensive description of the limitations of established theories on bound electronic nonlinearities in direct-gap semiconductors by performing various experiments on wide and narrow bandgap semiconductors along with developing theoretical models. Nondegenerate two-photon absorption (2PA) is studied in several semiconductors showing orders of magnitude enhancement over the degenerate counterpart. In addition, three-photon absorption (3PA) is studied in ZnSe and other semiconductors and a new theory using a Kane 4-band model is developed which fits new data well. Finally, the narrow gap semiconductor InSb is studied with regard to multiphoton absorption, free-carrier …
Search For Gas Giants Around Late-M Dwarfs,
2010
University of Central Florida
Search For Gas Giants Around Late-M Dwarfs, Rohit Deshpande
Electronic Theses and Dissertations
We carried out a near-infrared radial velocity search for Jupiter-mass planets around 36 late M dwarfs. This survey was the first of its kind undertaken to monitor radial velocity variability of these faint dwarfs. For this unique survey we employed the 10-m Keck II on Mauna Kea in Hawaii. With a resolution of 20,000 on the near-infrared spectrograph, NIRSPEC, we monitored these stars over four epochs in 2007. In addition to the measurement of relative radial velocity we established physical properties of these stars. The physical properties of M dwarfs we determined included the identification of neutral atomic lines, the …
Silicon-Sensitized Erbium Excitation In Silicon-Rich Silica For Integrated Photonics,
2010
University of Central Florida
Silicon-Sensitized Erbium Excitation In Silicon-Rich Silica For Integrated Photonics, Oleksandr Savchyn
Electronic Theses and Dissertations
It is widely accepted that the continued increase of processor performance requires at least partial replacement of electronic interconnects with their photonic counterparts. The implementation of optical interconnects requires the realization of a silicon-based light source, which is challenging task due to the low emission efficiency of silicon. One of the main approaches to address this challenge is the use of doping of silicon based matrices with optical centers, including erbium ions. Erbium ions incorporated in various hosts assume the trivalent state (Er3+) and demonstrate a transition at 1.54 μm, coinciding with optical transmission windows in both silicon and silica. …
Survey Of Meteorite Physical Properties Density, Porosity And Magnetic Susceptibility,
2010
University of Central Florida
Survey Of Meteorite Physical Properties Density, Porosity And Magnetic Susceptibility, Robert J. Macke
Electronic Theses and Dissertations
The measurement of meteorite physical properties (i.e. density, porosity, magnetic susceptibility) supplements detailed chemical and isotopic analyses for small samples (thin sections or ~300 mg portions) by providing whole-rock data for samples massing in the tens of grams. With the advent of fast, non-destructive and non-contaminating measurement techniques including helium ideal-gas pycnometry for grain density, the Archimedean ―glass bead‖ method for bulk density and (with grain density) porosity, and the use of low-field magnetometry for magnetic susceptibility, all of which rely on compact and portable equipment, this has enabled a comprehensive survey of these physical properties for a wide variety …
A Wearable Head-Mounted Projection Display,
2010
University of Central Florida
A Wearable Head-Mounted Projection Display, Ricardo F. Martins
Electronic Theses and Dissertations
Conventional head-mounted projection displays (HMPDs) contain of a pair of miniature projection lenses, beamsplitters, and miniature displays mounted on the helmet, as well as a retro-reflective screen placed strategically in the environment. We have extened the HMPD technology integrating the screen into a fully mobile embodiment. Some initial efforts of demonstrating this technology has been captured followed by an investigation of the diffraction effects versus image degradation caused by integrating the retro-reflective screen within the HMPD. The key contribution of this research is the conception and development of a mobileHMPD (M-HMPD). We have included an extensive analysis of macro- and …
Electron Transport In Molecular Systems,
2010
Michigan Technological University
Electron Transport In Molecular Systems, Haiying He
Dissertations, Master's Theses and Master's Reports - Open
The remarkable advances in nanoscience and nanotechnology over the last two decades allow one to manipulate individuals atoms, molecules and nanostructures, make it possible to build devices with only a few nanometers, and enhance the nano-bio fusion in tackling biological and medical problems. It complies with the ever-increasing need for device miniaturization, from magnetic storage devices, electronic building blocks for computers, to chemical and biological sensors. Despite the continuing efforts based on conventional methods, they are likely to reach the fundamental limit of miniaturization in the next decade, when feature lengths shrink below 100 nm. On the one hand, quantum …
Understanding The Promotion Effect: A Density Functional Theory Study Based On High Resolution Transmission Electron Microscopy Images For Mos2-Cobalt Promoted Interfaces,
2010
University of Texas at El Paso
Understanding The Promotion Effect: A Density Functional Theory Study Based On High Resolution Transmission Electron Microscopy Images For Mos2-Cobalt Promoted Interfaces, Manuel A. Ramos
Open Access Theses & Dissertations
Many studies had been done in order to understand promotion effect and structure/function in unsupported catalyst. Results indicated that d-electrons play an important role promoting catalytical active sites at the edges of MoS2 catalytically structures. Sulfur removal from crude oil, occurs on the edge of molybdenum di-sulfide (MoS2) nano structures, due to promotion of MoS2 nano structures with nickel or cobalt in sulfur-terminated or molybdenum-terminated edge planes. The promotion leads to formation of so-called CoMoS phase (MoS2/Co9S8) first discovered by meaning of Mössbauer spectroscopy, much more CoMoS phase usually called unsupported catalytical particles, have been topic of great interest in …
