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Full-Text Articles in Physics
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 …
Tunable Few- To Many-Cycle Source For High-Order Harmonic Generation And Time-Resolved Spectroscopy, John Beetar
Tunable Few- To Many-Cycle Source For High-Order Harmonic Generation And Time-Resolved Spectroscopy, John Beetar
Electronic Theses and Dissertations, 2020-
The temporal confinement of laser light pulses to durations approaching the optical period, and the subsequent conversion of these pulses into extreme ultraviolet and x-ray wavelengths through the process of high-order harmonic generation (HHG), has enabled measurement and control of ultrafast processes spanning picosecond to attosecond timescales. Typically achieved by nonlinear compression of multi-cycle pulses in gas-filled hollow-core fibers, compression to single-and even sub-cycle durations is now becoming routine due to the availability of state-of-the-art Ti:sapphire laser amplifiers outputting millijoule level pulses with pulse durations below ten cycles. Even so, reliance on mJ-level Ti:sapphire lasers has in most cases limited …
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 …
Wave-Optics Simulation Of Correlated Speckle Fields, Derek Burrell
Wave-Optics Simulation Of Correlated Speckle Fields, Derek Burrell
Electronic Theses and Dissertations, 2020-
Laser speckle poses an ongoing challenge to optical systems that utilize coherent light for active illumination, including applications in holography, free-space communications, remote sensing and target tracking. Speckle averaging offers one potential path forward by reducing the contrast, thereby boosting signal-to-noise ratios. This approach becomes limited, however, by the degree of correlation between successive frames. Wave-optics simulations help to characterize performance gains through speckle averaging, and so it is important that existing models properly account for decorrelation rates of dynamic speckle. With that goal in mind, this research seeks to build a suite of computational wave-optics experiments that verify speckle …
Experimental And Computational Investigation Of Plume Surface Interactions In Vacuum Microgravity, Wesley Chambers
Experimental And Computational Investigation Of Plume Surface Interactions In Vacuum Microgravity, Wesley Chambers
Electronic Theses and Dissertations, 2020-
Plume surface interactions (PSI) are caused by rocket exhaust impinging on planetary surfaces. PSI-induced environmental changes pose hazards to spacecraft and astronauts; thus, it is crucial to understand the gas-particle dynamics of these systems. We have conducted novel experimental and computational work to study PSI effects in relevant vacuum microgravity environments. To study flow effects and regolith instability we developed a computational model that describes the gas flow through a porous medium based on Darcy's Law. This flow depends on regolith properties, and the resulting subsurface pressure distribution is used to estimate ejecta mass. We find flow behaviors and the …
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 …
Discovery Of New Topological Quantum Materials By Photoemission, Md Mofazzel Hosen
Discovery Of New Topological Quantum Materials By Photoemission, Md Mofazzel Hosen
Electronic Theses and Dissertations, 2020-
A topological insulator (TI) is a novel electronic state of quantum matter characterize by a bulk insulating bandgap and spin-polarized metallic surface states. Recently, the idea of topology protected surface states extended to semimetallic/metallic systems such as Dirac and Weyl semimetals. Unlike topological insulators where only surface states are interesting and topologically protected, Dirac and Weyl semimetals feature unusual bands in both on the surface and bulk. Dirac semimetals show photon-like linear band dispersion and exhibit a variety of exotic properties that include surface Fermi arc, large magnetoresistance, and high carrier mobility, etc. Recently, a new type of topological phase …
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 …
Parallelized X-Ray Tracing With Gpu Ray-Tracing Engine, Joseph Ulseth
Parallelized X-Ray Tracing With Gpu Ray-Tracing Engine, Joseph Ulseth
Electronic Theses and Dissertations, 2020-
X-ray diffraction tomography (XDT) is used to probe material composition of objects, providing improved contrast between materials compared to conventional transmission based computed tomography (CT). In this work, a small angle approximation to Bragg's Equation of diffraction is coupled with parallelized computing using Graphics Processing Units (GPUs) to accelerate XDT simulations. The approximation gives rise to a simple yet useful proportionality between momentum transfer, radial distance of diffracted signal with respect to incoming beam's location, and depth of material, so that ray tracing may be parallelized. NVIDIA's OptiX ray-tracing engine, a parallelized pipeline for GPUs, is employed to perform XDT …
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 …
Characterization Of The Physical And Chemical Effect Of Membrane Disruption And Protein Inhibiting Treatments On E. Coli, Khadijah Wright
Characterization Of The Physical And Chemical Effect Of Membrane Disruption And Protein Inhibiting Treatments On E. Coli, Khadijah Wright
Honors Undergraduate Theses
The increase in antibacterial resistance has placed the issue of microbial multi-drug resistance on a global stage (Gurunathan, 2019). This issue poses a threat to human and animal health as well as to the environment (Aslam et al., 2018). It affects not only the efficacy of treatment but also how those treatments are conducted (Friedman, Temkin, & Carmeli, 2016). As a result of this ongoing threat, new treatments that have potent effects on bacteria are necessary. One scientific response to this issue has been the development of multifunctional nanoparticles (NPs)(H. Wang et al., 2018). NPs have the ability to be …
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 …
Polarization Dependence Of High Order Harmonic Generation From Solids In Reflection And Transmission Geometries, Erin L. Crites
Polarization Dependence Of High Order Harmonic Generation From Solids In Reflection And Transmission Geometries, Erin L. Crites
Honors Undergraduate Theses
High harmonic generation (HHG) is a process that occurs when an intense laser interacts with a material and generates new frequencies of light. HHG has many practical applications, namely as a spectroscopy technique and source for high frequency light and attosecond pulses. While HHG has been done extensively in gases, HHG in solids is a relatively new field. Solids are appealing as an HHG medium as they require much simpler equipment and are subsequently much more compact, and thus may have a variety of applications previously inaccessible to gas-phase HHG. However, the generation mechanism of HHG in solids has not …
High-Fidelity Mini-Led And Micro-Led Displays, Yuge Huang
High-Fidelity Mini-Led And Micro-Led Displays, Yuge Huang
Electronic Theses and Dissertations, 2020-
Mini-LED and micro-LED are emerging disruptive display technologies, because they can work as local dimmable backlight to significantly enhance the dynamic range of conventional LCDs, or as sunlight readable emissive displays. However, there are still unresolved issues impairing their display fidelity: 1) motion blur on high-resolution, large-size and high-luminance devices, 2) limited contrast ratio on mini-LED backlit LCD (mLED-LCD), 3) relatively high power consumption, and 4) compromised ambient contrast ratio. This dissertation tackles with each of these issues for achieving high display fidelity. Motion blur is caused by slow liquid crystal response time and image update delays. Low-duty ratio operation …
Multi-Parameter Optical Metrology: Quantum And Classical, Walker Larson
Multi-Parameter Optical Metrology: Quantum And Classical, Walker Larson
Electronic Theses and Dissertations, 2020-
The insights offered by quantum mechanics to the field of optical metrology are many-fold, with non-classical states of light themselves used to make sensors that surpass the sensitivity of sensors using classical states of light. Unfortunately, this advantage, referred to often as "super-sensitivity" is notoriously fragile, and even the slightest experimental imperfections may greatly reduce the efficacy of the non-classical sensors, sometimes completely obviating their advantage. In my thesis I have shown that the performance of an otherwise ideal two-photon interferometer, which exploits entanglement between photons to make super-sensitive measurements of phase, is crippled by the slightest introduction of decoherence …
Fluorescence Microscopy With Tailored Illumination Light, Jialei Tang
Fluorescence Microscopy With Tailored Illumination Light, Jialei Tang
Electronic Theses and Dissertations, 2020-
Fluorescence microscopy has long been a valuable tool for biological and medical imaging. Control of optical parameters such as the amplitude, phase, polarization and propagation angle of light gives fluorescence imaging great capabilities ranging from single molecule imaging to long-term observation of living organisms. While numerous fluorescence imaging techniques have been developed over the past decades, there is always an inevitable tradeoff among the spatial resolution, imaging speed, contrast, photodamage and the total cost when it comes to choose the appropriate microscope. A main goal of my dissertation research is to develop state-of-the-art microscope systems that exhibit unprecedented performance in …
Investigating The Inclusiveness Of Stem Courses And Reducing Barriers By Using The Universal Design For Learning Framework, Westley James
Investigating The Inclusiveness Of Stem Courses And Reducing Barriers By Using The Universal Design For Learning Framework, Westley James
Electronic Theses and Dissertations, 2020-
Students with disabilities are in postsecondary STEM courses and degree programs, but only a few studies have investigated how STEM courses can be designed to support students with disabilities. We began addressing this gap by interviewing students with diagnoses characterized by variations in executive functions about their experiences in postsecondary STEM courses. We analyzed the interviews through a social relational perspective of disability as this allowed us to identify how course structures disable students from effective engagement with STEM courses. We found STEM courses present heightened barriers compared to non-STEM courses, with common barriers including a lack of resources and …
Transient Mid-Ir Nonlinear Refraction In Air And Nonlinear Optical Properties Of Organometallic Complexes, Salimeh Tofighi
Transient Mid-Ir Nonlinear Refraction In Air And Nonlinear Optical Properties Of Organometallic Complexes, Salimeh Tofighi
Electronic Theses and Dissertations, 2020-
This dissertation explores two main topics: Transient nonlinear refraction of air in Mid-IR spectral range and nonlinear optical properties of organometallic complexes. For seeing a vibrational and rotational Raman response the molecule should be Raman active. The first requirement for being a Raman active molecule is that the polarizability of molecule must be anisotropic. Linear symmetric molecules do have rotational Raman spectra. Not all the vibrational mode can be excited by a femtosecond pulse. The pulsewidth of our excitation beam should be less than the half of the vibration period. In this dissertation my excitation pulsewidth is not short enough …