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Articles 61 - 90 of 575
Full-Text Articles in Physics
Analysis And Design Of Infrared Fiber Bundles For Large Field-Of-View Thermal Imaging, Cesar A. Lopez-Zelaya
Analysis And Design Of Infrared Fiber Bundles For Large Field-Of-View Thermal Imaging, Cesar A. Lopez-Zelaya
Honors Undergraduate Theses
During the DARPA SCENICC program, J. Ford, et al., demonstrated that CFBs provide a compelling route to compact, wide angle imagers. Monocentric lenses readily provide diffraction-limited images over wide field but onto a hemispherically curved image surface. They demonstrated visible CFBs can be tapered, cut and polished to relay curved images to flat sensors. We have shown that this provides a volumetric imaging efficiency a hundredfold larger than bulk optics can produce; a hundred times the resolution in the same volume or a hundred times less volume for the same resolution. Ford's work leveraged commercial fiber bundles available for the …
Dual Beam Frequency Comb Ftir Spectroscopy, Connor Kelly
Dual Beam Frequency Comb Ftir Spectroscopy, Connor Kelly
Electronic Theses and Dissertations, 2020-
A visible and Infrared (IR) range dual beam frequency comb Fourier transform spectrometer was developed. Using dual mode-locked Ti:Sapphire lasers a comb-interferogram was generated in the visible range. This spectrum was calculated and used to measure the transmittance of a Nd-doped crystal. The system was further developed to generate an IR interferogram by Difference Frequency Generation (DFG) using a Gallium Selenide (GaSe) crystal placed in the mode-locked pump beam. Numerical work was done to calculate the expected DFG spectrum confirming the necessary IR range can be reached. This has been conducted in support of an IR holographic spectroscopic microscopy spatial …
Measurement And Mitigation Of Optical, Recombination And Resistive Losses In Silicon Photovoltaics, Mohammad Jobayer Hossain
Measurement And Mitigation Of Optical, Recombination And Resistive Losses In Silicon Photovoltaics, Mohammad Jobayer Hossain
Electronic Theses and Dissertations, 2020-
Today, most of the photovoltaic cells in the market are made of silicon. Great achievements are being attained every year in terms of reducing the price of this kind of cells and improving their efficiency, reliability and durability. However, further improving the cell performance is a challenging task because of the presence of optical, recombination and resistive loss mechanisms in the cell. This work is focused on the measurement and mitigation of these losses. Mitigation of the optical, recombination and resistive losses at first require quantifying those losses and their impacts on the cell performance metrics accurately. Traditionally, solar cells …
Superconductivity And Topological Properties In A Topological Semimetal, K A M Hasan Siddiquee
Superconductivity And Topological Properties In A Topological Semimetal, K A M Hasan Siddiquee
Electronic Theses and Dissertations, 2020-
Topological superconductors (TSCs) in which superconductivity and topological properties are combined are characterized by topologically protected gapless states in the superconducting gaps. Realized in the gapless states of TSCs, Majorana fermions, which are particles and their own antiparticles, have crucial importance in quantum computation and spintronic device applications because of the exotic nature. Despite extensive study for the confirmation of TSCs, the observation of Majorana fermions in bulk superconductors has not been settled yet. Recently, the binary stannide semimetal CaSn3 with a cubic structure has been proposed to be a promising candidate for realizing topological superconductivity. In this dissertation, to …
Understanding The Mechanisms Of Surface Chemical Reactions By Tracking Unstable Intermediate Species, Md Afjal Khan Pathan
Understanding The Mechanisms Of Surface Chemical Reactions By Tracking Unstable Intermediate Species, Md Afjal Khan Pathan
Electronic Theses and Dissertations, 2020-
The detection of intermediate species formed during surface chemical reactions is essential because it can provide critical information about the reaction mechanisms at surfaces and interfaces. Therefore, the overarching goal of this research was to understand the mechanisms of surface catalytic, photocatalytic, and photoinduced reactions by monitoring the intermediate species formed during these reactions. To understand the initial steps of the carbon monoxide hydrogenation reaction on two-dimensional (2D) MoS2 and TaS2 materials, temperature programmed desorption and reaction are employed. Large-area 2D-MoS2 and 2D-TaS2 were prepared on a Cu(111) substrate under ultra-high vacuum conditions via physical vapor deposition. The highly crystalline …
Plasmonic Properties Of Nanopatterned Graphene, Muhammad Waqas Shabbir
Plasmonic Properties Of Nanopatterned Graphene, Muhammad Waqas Shabbir
Electronic Theses and Dissertations, 2020-
Graphene is an atomically thin two-dimensional material with carbon atoms arranged in a honeycomb lattice. It has been successfully mechanically exfoliated from graphite and characterized in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, UK. While suspended graphene holds the world record in mobility exceeding 100,000 cm2/Vs, which means that graphene could increase the operating frequency of electronic devices up to the THz regime. For example, imaging computer chips running at a few THz frequency, which would be about 1000 times faster than current chips. However, there are two main obstacles for using graphene in electronics …
On The Information Content In Unresolved Imaging, Zhean Shen
On The Information Content In Unresolved Imaging, Zhean Shen
Electronic Theses and Dissertations, 2020-
Imaging is almost synonymous with optics. Imaging is the process of using light to form a tangible or visible representation, an imitation (imitari) of a material property. There are many situations, however, where one can only aspire to 'sense making' rather than forming an image per se. In other words, objects cannot be directly resolved by conventional intensity-based imaging, a situation commonly referred to as 'unresolved imaging'. However, there is still information retained in other properties of light, which can be exposed by other means. In this thesis I will discuss two typical situations: subwavelength and multiple scattering, which are …
Photoemission Investigation Of Topological Quantum Materials, Klauss M. Dimitri
Photoemission Investigation Of Topological Quantum Materials, Klauss M. Dimitri
Honors Undergraduate Theses
Topological insulators (TIs) are a class of quantum materials, which behave as insulators in the bulk, yet possess gapless spin-polarized surface states, which are robust against nonmagnetic impurities. The unique properties of TIs make them attractive not only for studying various fundamental phenomena in condensed matter and particle physics, but also as promising candidates for applications ranging from spintronics to quantum computation. Within the topological insulator realm, a great deal of focus has been placed on discovering new quantum materials, however, ideal multi-modal quantum materials have yet to be found. Here we study alpha-PdBi2, KFe2Te2, and DySb compounds including others …
Chemical Vapor Deposition Growth Of Transition Metal Dichalcogenides And Their Heterostructure Integration, Sajeevi Sankalpani Withanage
Chemical Vapor Deposition Growth Of Transition Metal Dichalcogenides And Their Heterostructure Integration, Sajeevi Sankalpani Withanage
Electronic Theses and Dissertations, 2020-
Two-dimensional transition metal dichalcogenides (TMDs) are of great interest for the discovery of many novel physics owing to their extraordinary electrical, optical, mechanical properties as well as many promising applications including heterojunctions. To realize the overreaching goals of these materials, it is important to develop scalable growth techniques and investigate the role of different growth parameters on the resulting material properties. In this dissertation, I study, (i) controllable and reproducible growth of monolayer molybdenum disulfide (MoS2) via chemical vapor deposition (CVD), (ii) the role of growth temperature on the properties of large area MoS2 thin films grown via thermal vapor …
Structure Of Unmodified And Pyroglutamylated Amyloid Beta Peptide In Lipid Membranes, Rowan Hassan
Structure Of Unmodified And Pyroglutamylated Amyloid Beta Peptide In Lipid Membranes, Rowan Hassan
Honors Undergraduate Theses
Alzheimer's Disease (AD) is a devastating neurodegenerative disease that is characterized by brain atrophy, neuronal and synaptic loss, cognitive decline, trouble handling activities of daily life, and ultimately leads to death. Worldwide, at least 30 million people suffer from AD, with 5.8 million suffering in the US alone. Despite extensive basic and clinical research, the underlying molecular mechanisms behind AD remain largely unknown. There are four FDA-approved compounds are used for alleviating symptoms but have no curative potency. The first potentially disease-modifying AD drug, aducanumb, was approved by FDA in June 2021. The main histopathological traits of AD are the …
Liquid Crystal Flat Optics For Near-Eye Displays, Tao Zhan
Liquid Crystal Flat Optics For Near-Eye Displays, Tao Zhan
Electronic Theses and Dissertations, 2020-
Augmented reality (AR) and virtual reality (VR) displays, considered as the next-generation information platform, have shown great potential to revolutionize the way how we interact with each other and the digital world. Both AR and VR are disruptive technologies that can enable numerous applications in education, healthcare, design, training, entertainment, and engineering. Among all the building blocks of these emerging devices, near-eye displays (NEDs) play a critical role in the entire system, through which we can perceive the virtual world as the real one. However, the visual experience offered by existing NED technologies is still far from satisfying the human …
High Speed Modulation Characteristics Of Semiconductor Nanolasers And Coupled Ring Laser Systems, Chi Xu
High Speed Modulation Characteristics Of Semiconductor Nanolasers And Coupled Ring Laser Systems, Chi Xu
Electronic Theses and Dissertations, 2020-
Optical communication systems require light sources that can be modulated with high speeds. However, the modulation bandwidth of laser diodes is typically limited by an intrinsic value, its relaxation resonance frequency. In order to circumvent this limitation, a number of methods have been proposed to boost the modulation speed, including optical injection locking, quantum dots lasers with large differential gain, push-pull modulation in composite lasers. This dissertation explores two new approaches for enhancing the direct modulation bandwidth of semiconductor quantum well laser diodes. Lasers with strong spontaneous emission have been shown to exhibit a high-speed performance theoretically. It is expected …
Tensor Network States: Optimizations And Applications In Quantum Many-Body Physics And Machine Learning, Justin Reyes
Tensor Network States: Optimizations And Applications In Quantum Many-Body Physics And Machine Learning, Justin Reyes
Electronic Theses and Dissertations, 2020-
Tensor network states are ubiquitous in the investigation of quantum many-body (QMB) physics. Their advantage over other state representations is evident from their reduction in the computational complexity required to obtain various quantities of interest, namely observables. Additionally, they provide a natural platform for investigating entanglement properties within a system. In this dissertation, we develop various novel algorithms and optimizations to tensor networks for the investigation of QMB systems, including classical and quantum circuits. Specifically, we study optimizations for the two-dimensional Ising model in a transverse field, we create an algorithm for the $k$-SAT problem, and we study the entanglement …
Theoretical Analysis Of The Conduction Properties Of Self Assembled Molecular Tunnel Junctions, Cameron Nickle
Theoretical Analysis Of The Conduction Properties Of Self Assembled Molecular Tunnel Junctions, Cameron Nickle
Electronic Theses and Dissertations, 2020-
As the size scale of electrical devices approach the atomic scale. Moore's law is predicted to be over for semiconductor devices. Studies into the replacement of semiconductor technology with organic devices was first predicted by Avriam and Ratner[1] in 1974. Since then significant research into molecular based organic devices has been conducted. The work presented in this dissertation explores the theoretical frameworks used to model transport through molecular junctions. We present studies which seek to garner a better understanding of the charge transport through molecular junctions and how the conduction properties can be optimized. We show that a single atom …
Atomic Scale Processes And Electronic Band Structure Engineering In Thin Layered Materials, Brandon Blue
Atomic Scale Processes And Electronic Band Structure Engineering In Thin Layered Materials, Brandon Blue
Electronic Theses and Dissertations, 2020-
In this work, a variety of layered materials are considered for their potential technologic applications and the role of structure on the physical properties of the material system as a whole. Transition metal dichalcogenides form the core of the work discussed here, with additional results from an iron pnictide-based superconductor and for a biologically-sourced proton conductor. Here, a commercial scanning tunneling microscope (STM) with liquid cryogenic cooling provides information about both the atomic-scale structure of the surface and the local electronic density of states (LDOS) as a function of position. The interplay of superconducting and charge-density wave states is discussed …
The Physical Properties Of Asteroids, Leos Pohl
The Physical Properties Of Asteroids, Leos Pohl
Electronic Theses and Dissertations, 2020-
The Small Bodies of the Solar System are leftover material from the formation of planets. Compared with planetary bodies, they have undergone little transformation. Embedded in their physical properties, they provide clues to the conditions and processes that took place since the condensation of the Solar Nebula. Furthermore, asteroids are sources of raw materials that are becoming more costly to obtain from the interior of the Earth. The possibilities of extracting those materials has become a topic of significant interest. In this dissertation, I explore several properties of asteroid material: strength of asteroids, their shielding properties against high energetic particles …
Predicting Structures Of 2d Materials Enabled By Machine Learning, Sonali Joshi
Predicting Structures Of 2d Materials Enabled By Machine Learning, Sonali Joshi
Honors Undergraduate Theses
Prediction of stable structures of two-dimensional (2D) materials that have not been experimentally realized is an important pre-requisite step for the development of these materials for various technological uses without the extensive trial-error experiments. Traditional methods such as density functional theory (DFT) can be used to find the energies of structures computationally, however, calculating the energies of the total number of structures possible would be daunting timewise as well. We propose using machine learning methods to reduce the search time for 2D materials’ geometric structures. Our case study for this process consists of hexagonal graphene-like boron–carbon–nitrogen (h-BCN). Our …
Nonlinear Optical Mechanisms In Semiconductors And Enhanced Nonlinearities At Epsilon-Near-Zero, Sepehr Ahmadzadeh Benis
Nonlinear Optical Mechanisms In Semiconductors And Enhanced Nonlinearities At Epsilon-Near-Zero, Sepehr Ahmadzadeh Benis
Electronic Theses and Dissertations, 2020-
Light does not interact with itself in linear optical materials. Such interactions occur only in non-linear optical (NLO) materials and typically require high intensity optical beams to be signifi-cant. The ever-increasing role of NLO, where intense light may change the properties of the me-dium, has created a pressing demand to invent materials for achieving more efficient light-light and light-matter interaction due to their potential capacity to augment and possibly replace cur-rent technologies with more efficient devices. There are numerous applications of NLO devices in fundamental science, technology, health, and defense such as all-optical computation and sig-nal processing, ultrashort laser technology, …
Attosecond Transient Absorption Spectroscopy In The Water Window, Andrew Chew
Attosecond Transient Absorption Spectroscopy In The Water Window, Andrew Chew
Electronic Theses and Dissertations, 2020-
The push to study the atomic and molecular dynamics at ever smaller time scales has been the main driving force for developing laser systems with ever shorter pulse durations. Thus far, picosecond lasers and femtosecond lasers have been used with great success in femtochemistry to study molecular dynamics such as molecular rotation and vibration, which all occur in the tens to hundreds of femtosecond. To study electron dynamics however, which are on the order of attoseconds, one needs attosecond laser sources to be able to have the time resolution required to probe ultrafast electron dynamics such as AC Stark shifts, …
Theoretical Studies Of Collisions Involving Three Bodies And Electron-Molecule Collisions Relevant To Astrophysical And Atmospheric Conditions, Chi Hong Yuen
Electronic Theses and Dissertations, 2020-
Accurate rate coefficients of atomic and molecular processes allow us to probe the conditions in space and understand the history of the Universe. Although experimental rate coefficients are the most desirable, availability of accurate rate coefficients of some processes depends on rigorous theoretical studies. In this dissertation, theoretical tools for collisions involving three bodies are discussed and applied to three different reactions. Rate coefficient of the reactive scattering of H2 + D- is computed using the ABC program. The present results are about ten times smaller than the experimental upper limit, suggesting that a further improvement of the sensitivity of …
Novel Fibers And Components For Space Division Multiplexing Technologies, Juan Carlos Alvarado Zacarias
Novel Fibers And Components For Space Division Multiplexing Technologies, Juan Carlos Alvarado Zacarias
Electronic Theses and Dissertations, 2020-
Passive devices and amplifiers for space division multiplexing are key components for future deployment of this technology and for the development of new applications exploring the spatial diversity of light. Some important devices include photonic lantern (PL) mode multiplexers supporting several modes, fan-in/fan-out (FIFO) devices for multicore fibers (MCFs), and multimode amplifiers capable of amplifying several modes with low differential modal gain penalty. All these components are required to overcome the capacity limit of single mode fiber (SMF) communication systems, driven by the growing data capacity demand. In this dissertation I propose and develop different passive components and amplifiers for …
Iterative Optical Diffraction Tomography For Reconstruction Of Multiply-Scattering Objects, Shengli Fan
Iterative Optical Diffraction Tomography For Reconstruction Of Multiply-Scattering Objects, Shengli Fan
Electronic Theses and Dissertations, 2020-
As a label-free, non-destructive, high-resolution, and quantitative imaging technique, optical diffraction tomography (ODT) has been widely used to image biological samples and microstructures, such as cells, tissues, and optical fibers. The refractive-index (RI) distribution of an object is reconstructed from multi-view measurements of diffracted fields emerging from the object. Typical ODT setups include the object rotating configuration (ORC) and the illumination scanning configuration (ISC). One major limitation of ODT is that it is only applicable to weakly-scattering objects. In this dissertation, novel methods have been developed to overcome the reconstruction difficulty caused by multiple scattering, so as to extend ODT …
Midwave Vs Longwave Infrared Search And Track And Aerosol Scattering Target Acquisition Performance, Steven Butrimas
Midwave Vs Longwave Infrared Search And Track And Aerosol Scattering Target Acquisition Performance, Steven Butrimas
Electronic Theses and Dissertations, 2020-
The decision on whether to use a mid wave infrared (MWIR) or long wave infrared (LWIR) sensor for a given task can be a formidable verdict. The scope entails facts about the observable source, the atmospheric interactions, and the sensor parameters within the hardware device. Even when all the individual metrics are known, the combination ultimately determines whether a MWIR or LWIR sensor is more appropriate. Despite the vast number of variables at play, the reduction of inputs through focused studies can provide essential insight into MWIR and LWIR comparisons. This dissertation focuses on the roles of point source target …
Symmetry And High Harmonic Spectroscopy In Solids, Shima Gholam Mirzaeimoghadar
Symmetry And High Harmonic Spectroscopy In Solids, Shima Gholam Mirzaeimoghadar
Electronic Theses and Dissertations, 2020-
High harmonic generation (HHG) by intense femtosecond laser pulses has, over the last three decades, provided new coherent sources of extreme ultraviolet and soft x-ray light and enabled the field of attosecond science. Furthermore, as properties of the target are encoded in the harmonic emission, high harmonic spectroscopy has allowed extraction of molecular structure and dynamics from the spectra and polarization states of harmonics generated from gas-phase molecules. HHG from solids, discovered in 2011, now promises to offer similar benefits to condensed matter physics. In this dissertation, I describe progress on two fronts: extending attosecond techniques to generate new high …
Heterogeneous Integrated Photonics For Nonlinear Frequency Conversion And Polarization Diversity, Tracy Sjaardema
Heterogeneous Integrated Photonics For Nonlinear Frequency Conversion And Polarization Diversity, Tracy Sjaardema
Electronic Theses and Dissertations, 2020-
Silicon has proven to be one of the materials of choice for many integrated photonic applications. However, silicon photonics is limited by certain material shortcomings. Two shortcomings addressed in this work are zero second-order optical nonlinearity, and the lack of methods available to achieve broadband polarization diversity. Heterogeneous integrated solutions for these shortcomings of silicon photonics are presented in this work. First, nonlinear frequency conversion is demonstrated with thin-film lithium niobate on silicon substrates. The method for reaching the highest-achieved second-harmonic generation conversion efficiency, using active monitoring during periodic poling, is discussed. Additionally, a cascaded approach for generating higher-order harmonics …
High Performance Micro-Scale Light Emitting Diode Display, Fangwang Gou
High Performance Micro-Scale Light Emitting Diode Display, Fangwang Gou
Electronic Theses and Dissertations, 2020-
Micro-scale light emitting diode (micro-LED) is a potentially disruptive display technology because of its outstanding features such as high dynamic range, good sunlight readability, long lifetime, low power consumption, and wide color gamut. To achieve full-color displays, three approaches are commonly used: 1) to assemble individual RGB micro-LED pixels from semiconductor wafers to the same driving backplane through pick-and-place approach, which is referred to as mass transfer process; 2) to utilize monochromatic blue micro-LED with a color conversion film to obtain a white source first, and then employ color filters to form RGB pixels, and 3) to use blue or …
Space Weathering Simulation Trends On Carbonaceous Chondrites, Andrew Malfavon
Space Weathering Simulation Trends On Carbonaceous Chondrites, Andrew Malfavon
Electronic Theses and Dissertations, 2020-
Space weathering on primitive asteroids is an ongoing area of research. Primitive asteroids have low geometric albedo (= 0.15) and mostly featureless visible spectra (~0.5 - 0.9 µm) (Campins et al. 2018). Higher albedo S-type asteroids and their corresponding meteorites, ordinary chondrites, have well-characterized space weathering effects. The generally lower albedo primitive asteroids and their less common corresponding meteorites, carbonaceous chondrites, have shown various, sometimes disagreeing results in laboratory simulations. Experiments simulating solar wind exposure on carbonaceous chondrites by Lantz et al. (2017) and Nakamura et al. 2019 showed complex trends on different types of meteorite samples. Thompson et al. …
Few-Mode Fiber Lasers And Amplifiers, Ning Wang
Few-Mode Fiber Lasers And Amplifiers, Ning Wang
Electronic Theses and Dissertations, 2020-
Lasers and amplifiers of high-order spatial modes are useful for a number of applications, including communication, sensing, microscopy, and laser material processing. This dissertation presents the generation and amplification of high-order spatial modes in few-mode fibers (FMFs). In the area of amplification of high-order spatial modes, low-crosstalk amplification among spatial modes is realized in a retro-reflecting few-mode Er-doped fiber amplifier (EDFA) by exploiting the unitary property of the coupling matrix of a symmetric photonic lantern (PL). A small-signal gain larger than 25 dB and crosstalk below -10 dB was achieved over the C-band for a 3-mode EDFA. Such a few-mode …
Preparation And Characterization Of Epitaxial Thin Films With Applications In Catalysis And Microelectronics, Asim Khaniya
Preparation And Characterization Of Epitaxial Thin Films With Applications In Catalysis And Microelectronics, Asim Khaniya
Electronic Theses and Dissertations, 2020-
Ubiquitous in the modern world, the epitaxial thin film offers a wide range of practical applications in the field of microelectronics, solar industries, optical devices, and catalysis. This thesis deals with studying the growth and characterization of molybdenum nitride (MoN) and various dielectric encapsulated Ru(0001) thin films on single-crystal substrates. The phase-specific and single-crystalline MoN film was grown epitaxially on pre-nitrogen-covered Ru(0001) via physical vapor deposition and characterized by UHV based surface science analytical techniques, including X-ray photoelectron spectroscopy, helium ion scattering spectroscopy, auger electron spectroscopy, and low energy electron diffraction (LEED). The annealing temperature of 700 K was found …
Development Of High-Power Single-Mode Yb-Doped Fiber Amplifiers And Beam Analysis, Steffen Wittek
Development Of High-Power Single-Mode Yb-Doped Fiber Amplifiers And Beam Analysis, Steffen Wittek
Electronic Theses and Dissertations, 2020-
High-power fiber laser systems enjoy a widespread use in manufacturing, medical, and defense applications as well as scientific research, due to their remarkable power scalability, high electrical to optical efficiency, compactness and ruggedness. However, single-mode fiber power scaling has stagnated in the past years, primarily due to the onset of nonlinear effects such as stimulated Brillouin/Raman scattering and transverse modal instabilities. This thesis addresses the analysis and mitigation of transverse modal instabilities in high-power fiber amplifiers. I describe the high-power fiber amplifier testbed that I set up to test fibers fabricated in house. I will show our results of a …