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Articles 31 - 60 of 417

Full-Text Articles in Physics

Generation Of High-Flux Attosecond Pulses And Towards Attosecond-Attosecond Pump-Probe Experiments, Yang Wang Jan 2017

Generation Of High-Flux Attosecond Pulses And Towards Attosecond-Attosecond Pump-Probe Experiments, Yang Wang

Electronic Theses and Dissertations

At present, the energy of a single isolated attosecond pulse is limited to nanojoule levels. As a result, an intense femtosecond pulse has always been used in combination with a weak attosecond pulse in time-resolved experiments. To reach the goal of conducting true attosecond pump-attosecond probe experiments, a high flux laser source has been developed that can potentially deliver microjoule level isolated attosecond pulses in the 50 eV range, and a unique experimental end station has been fabricated and implemented that can provide precision control of the attosecond-attosecond pump-probe pulses. In order to scale up the attosecond flux, a unique ...


High Dynamic Range Display Systems, Ruidong Zhu Jan 2017

High Dynamic Range Display Systems, Ruidong Zhu

Electronic Theses and Dissertations

High contrast ratio (CR) enables a display system to faithfully reproduce the real objects. However, achieving high contrast, especially high ambient contrast (ACR), is a challenging task. In this dissertation, two display systems with high CR are discussed: high ACR augmented reality (AR) display and high dynamic range (HDR) display. For an AR display, we improved its ACR by incorporating a tunable transmittance liquid crystal (LC) film. The film has high tunable transmittance range, fast response time, and is fail-safe. To reduce the weight and size of a display system, we proposed a functional reflective polarizer, which can also help ...


High Power Fiber Lasers And Fiber Devices, Zeinab Sanjabieznaveh Jan 2017

High Power Fiber Lasers And Fiber Devices, Zeinab Sanjabieznaveh

Electronic Theses and Dissertations

Fiber lasers and fiber amplifiers have experienced considerable improvements in recent years and demonstrated remarkable power scalability. However, due to high optical intensity in the core, the performance of high power fiber lasers is limited by detrimental nonlinear processes, such as four-wave mixing, self-phase modulation, stimulated Brillouin scattering, and stimulated Raman scattering. To mitigate nonlinear effects, very large mode area (LMA) fibers, which exhibit a mode field diameter larger than 30 ?m have been developed. However, for larger core sizes the discrimination capabilities of conventional fiber designs decrease, consequently, LMA fibers are not strictly single mode which ultimately at high ...


Growth And Doping Of Mos2 Thin Films For Electronic And Optoelectronic Applications, Hussain Abouelkhair Jan 2017

Growth And Doping Of Mos2 Thin Films For Electronic And Optoelectronic Applications, Hussain Abouelkhair

Electronic Theses and Dissertations

MoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning electron microscope images revealed the growth of microdomes of MoS2 on top of a smooth MoS2 film. These microdomes are very promising as a broadband omnidirectional light trap ...


The Consequences Of A Reduced Superlattice Thickness On Quantum Cascade Laser Performance, Pedro Figueiredo Jan 2017

The Consequences Of A Reduced Superlattice Thickness On Quantum Cascade Laser Performance, Pedro Figueiredo

Electronic Theses and Dissertations

Coherent infrared radiation sources are essential for the operability of a wide range of scientific, industrial, military and commercial systems. The importance of the mid-infrared spectral region cannot be understated. Numerous molecules have some vibrational band in this range, allowing for identification of species by means of absorption, emission or some other form of spectroscopy. As such, spectroscopy alone has numerous applications ranging from industrial process control to disease diagnosis utilizing breath analysis. However, despite the discovery of the LASER in the 60s, to this day the amount of coherent sources in this range is limited. It is for this ...


Quantification Of Non-Stoichiometry And Impurities In Transparent Yag Ceramics By Laser-Induced Breakdown Spectroscopy (Libs), Sudeep Pandey Jan 2017

Quantification Of Non-Stoichiometry And Impurities In Transparent Yag Ceramics By Laser-Induced Breakdown Spectroscopy (Libs), Sudeep Pandey

Electronic Theses and Dissertations

Transparent ceramics are an important class of optical materials with applications in street-lighting, high-strength windows, electro- and magneto-optical isolators, high-power laser gain media and nuclear radiation detectors. Compared to single-crystal growth, ceramic processing enables size scalability, near net-shape forming and prevents issues associated with dopant segregation and inhomogeneity, such as stress-induced birefringence and wavefront distortions. The fabrication of high optical grade ceramics by route of powder sintering, relies on a controlled set of techniques preventing the formation of scattering centers (pores and secondary phases) and harmful point defects (color centers, charge-carrier trapping sites). This thesis work investigates a novel approach ...


Noise, Stability, And Linewidth Performance Of 10-Ghz Optical Frequency Combs Generated From The Nested Cavity Architecture, Kristina Bagnell Jan 2017

Noise, Stability, And Linewidth Performance Of 10-Ghz Optical Frequency Combs Generated From The Nested Cavity Architecture, Kristina Bagnell

Electronic Theses and Dissertations

Optical frequency combs with wide mode spacing and low timing jitter are relied upon for both time domain and frequency domain applications. It has been previously demonstrated that surrounding a low-Q semiconductor laser chip with a long external fiber cavity and inserting a high finesse Fabry–Pérot etalon into this cavity can produce a mode-locked laser with the desired high repetition rate and narrow optical mode linewidths which are of benefit to applications like photonic analog-to-digital conversion and astronomical spectrograph calibration. With this nested cavity architecture, the quality factor of the resonator is effectively determined by the product of the ...


Harnessing Spatial Intensity Fluctuations For Optical Imaging And Sensing, Milad Akhlaghi Bouzan Jan 2017

Harnessing Spatial Intensity Fluctuations For Optical Imaging And Sensing, Milad Akhlaghi Bouzan

Electronic Theses and Dissertations

Properties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing methodologies that use statistical properties of optical fluctuations for gauging specific information. We examine this concept in the context of three different aspects of computational optical imaging and sensing ...


Design And Verification Of A Multi-Terawatt Ti-Sapphire Femtosecond Laser System, Patrick Roumayah Jan 2017

Design And Verification Of A Multi-Terawatt Ti-Sapphire Femtosecond Laser System, Patrick Roumayah

Electronic Theses and Dissertations

Ultrashort pulse lasers are well-established in the scientific community due to the wide range of applications facilitated by their extreme intensities and broad bandwidth capabilities. This thesis will primarily present the design for the Mobile Ultrafast High Energy Laser Facility (MU-HELF) for use in outdoor atmospheric propagation experiments under development at the Laser Plasma Laboratory at UCF. The system is a 100fs 500 mJ Ti-Sapphire Chirped-Pulse Amplification (CPA) laser, operating at 10 Hz. Some background on the generation of very high intensity optical pulses is also presented, alongside an overview of the physics of filamentation. As part of the design ...


Development Of A Compact Broadband Optical Parametric Oscillator For Ultra-Sensitive Molecular Detection, Sean O. Crystal Jan 2017

Development Of A Compact Broadband Optical Parametric Oscillator For Ultra-Sensitive Molecular Detection, Sean O. Crystal

Honors Undergraduate Theses

Every gas molecule has a unique absorption spectrum that can be captured using optical spectroscopy to identify an unknown sample's composition. Frequency combs systems can provide an extremely broad mid-infrared spectrum that is very useful for molecular detection. A degenerate optical parametric oscillator (OPO) was built to generate the down-converted and shifted frequency comb spectrum. This system utilizes an ultra-short pulse 1.56µm pump laser and a never before used orientation patterned gallium-phosphide crystal. Periodically polled lithium niobate (PPLN), Gallium Arsenide (GaAs) and Gallium Phosphide are all crystals used to accomplish this task. GaP, in comparison to PPLN, has ...


Computational Approach To Electrocatalysis, Nagendra Dhakal Jan 2017

Computational Approach To Electrocatalysis, Nagendra Dhakal

Electronic Theses and Dissertations

The main objective of this work is to understand the theoretical basis of the working principle of the Hydrogen fuel cell. We seek the physical basis of the Rational Design Technique, the smart way of preselecting materials from the material-pool, implemented in our study anticipating highly promising electrocatalysts for promoting the conversion of chemical energy stored in hydrogen molecules into the electrical energy. It needs the understanding of the relationship among the compositions of the materials under consideration, their electronic structure and catalytic activities. We performed the first principle DFT calculations to achieve the goal. Our work is focused first ...


Theoretical Study Of Negative Molecular Ions Relevant To The Interstellar And Laboratory Plasma, Marjan Khamesian Jan 2017

Theoretical Study Of Negative Molecular Ions Relevant To The Interstellar And Laboratory Plasma, Marjan Khamesian

Electronic Theses and Dissertations

Recently, several negative molecular ions, CnN- (n = 1, 3, 5) and CnH- (n = 4, 6, 8), were observed in the interstellar medium (ISM). It was suggested that the anions are formed in the ISM by the process of radiative electron attachment (REA). A simple statistical model was developed in 1980's to estimate rate coefficients of the REA reactions. Some of the rate coefficients obtained in the model are consistent with the observations, the others are not. More importantly, some of the approximations employed in the model are not physically justified. The aim of this thesis is a development of ...


Using Low-Coherence Interferometry To Monitor Cell Invasion In An In-Vitro Model System, Behnaz Davoudi Nasab Jan 2017

Using Low-Coherence Interferometry To Monitor Cell Invasion In An In-Vitro Model System, Behnaz Davoudi Nasab

Honors Undergraduate Theses

In an optically random system, such as naturally occurring and man-made media, light undergoes pronounced multiple scattering. This phenomenon has shown a remarkable potential in characterizing complex materials. In this regime, scattering occurs from each individual center of the scattering and independent scattering events lead to multiple light scattering. This phenomenon is often described as a random walk of photons and can be modeled in terms of a diffusion equation based on the radiative transfer theory. In this thesis, we used optical path-length spectroscopy (OPS), which is an experimental method to obtain the path-length probability density of the propagating light ...


Temperature Dependence Of Dynamical Spin Injection In A Superconducting Niobium Thin Film, Tyler S. Townsend Jan 2017

Temperature Dependence Of Dynamical Spin Injection In A Superconducting Niobium Thin Film, Tyler S. Townsend

Honors Undergraduate Theses

Spintronics is a research field that focuses on the manipulation of the quantum mechanical spin of charge carriers in solid state materials for future technological applications. Creating large spin currents with large relaxation times is sought after in the field of spintronics which may be aided by combining spintronics with superconductivity. This thesis provides a phenomological study of the effective change in ferromagnetic resonance linewidth, by dynamical spin injection into a permalloy-copper-niobium tri-layer in the superconducting state. The ferromagetic resonance linewidth was measured from 2-14 K. It was observed that there was a change in the behavior of the resonance ...


Advanced Liquid Crystal Displays With Supreme Image Qualities, Haiwei Chen Jan 2017

Advanced Liquid Crystal Displays With Supreme Image Qualities, Haiwei Chen

Electronic Theses and Dissertations

Several metrics are commonly used to evaluate the performance of display devices. In this dissertation, we analyze three key parameters: fast response time, wide color gamut, and high contrast ratio, which affect the final perceived image quality. Firstly, we investigate how response time affects the motion blur, and then discover the 2-ms rule. With advanced low-viscosity materials, new operation modes, and backlight modulation technique, liquid crystal displays (LCDs) with an unnoticeable image blur can be realized. Its performance is comparable to an impulse-type display, like cathode ray tube (CRT). Next, we propose two novel backlight configurations to improve an LCD ...


Atomic-Scale Simulation Of Physical And Chemical Processes During Space Weathering And Planet Formation, Abrar Quadery Jan 2017

Atomic-Scale Simulation Of Physical And Chemical Processes During Space Weathering And Planet Formation, Abrar Quadery

Electronic Theses and Dissertations

We investigate the mechanisms of space weathering and dust grain collisions, two topics of interests from planetary sciences, using atomic-scale simulations. Space weathering is the change in chemical and physical properties of minerals exposed to solar radiation and micrometeorite bombardment on surfaces of airless planetary bodies like the Moon and asteroids. An understanding of the connection between the surface evolution of the minerals and the underlying thermodynamic and kinetic factors is still missing. We address this issue and determine the time evolution of Frenkel defects in the silicate minerals olivine ((Mg,Fe)$_2$SiO$_4$) and orthopyroxene ((Mg,Fe)SiO ...


Laser-Induced Crystallization Mechanisms In Chalcogenide Glass Materials For Advanced Optical Functionality, Laura Sisken Jan 2017

Laser-Induced Crystallization Mechanisms In Chalcogenide Glass Materials For Advanced Optical Functionality, Laura Sisken

Electronic Theses and Dissertations

Glass-ceramics (GC) are promising candidates for gradient refractive index (GRIN) optics. These multi-phase, composite materials also exhibit improved physical properties as compared to the parent base glass resulting from the formation of a secondary crystalline phase(s). Nanocrystal phase formation in a multi-component chalcogenide glass (ChG), (GeSe2-3As2Se3)(1-x)-(PbSe)x glass where x = 0-40 has been investigated, and the role of the starting material morphology has been correlated to the resulting composite's optical properties including refractive index, transmission, dispersion, and thermo-optic coefficient. Optical property evolution was related to the type and amount of the crystal phases formed, since through ...


The Physical Properties And Composition Of Main-Belt Asteroids From Infrared Spectroscopy, Zoe Landsman Jan 2017

The Physical Properties And Composition Of Main-Belt Asteroids From Infrared Spectroscopy, Zoe Landsman

Electronic Theses and Dissertations

Asteroids are the remnants of planet formation, and as such, they represent a record of the physical and chemical conditions in the early solar system and its evolution over the past 4.6 billion years. Asteroids are relatively accessible by spacecraft, and thus may be a source of the raw materials necessary for future human exploration and settlement of space. Those on Earth-crossing orbits pose impact hazards for which mitigation strategies must be developed. For these reasons, several missions to asteroids are in progress or planned with the support of the National Aeronautics and Space Administration (NASA) and other national ...


Spherical Self-Assembly Of Rous Sarcoma Virus Ca, Probed By Ssnmr And The Structure Of Pap And Reflectin Protein, Xin Qiao Jan 2017

Spherical Self-Assembly Of Rous Sarcoma Virus Ca, Probed By Ssnmr And The Structure Of Pap And Reflectin Protein, Xin Qiao

Electronic Theses and Dissertations

In this dissertation, we investigate the morphology of three different protein assemblies, which are formed by prostate acidic phosphatase, residues 248-286 (PAP39), reflectin and rous sarcoma virus capsid (RSV CA). First of all, the main aim of this research is to study the structure of PAP39 which is derived from protease cleavage of Prostate Acidic Phosphatase. The PAP39 can form fibrils of different morphologies in phosphate-buffered saline (PBS) and NaBiCarb (25 mM sodium bicarbonate and 40 mM sodium phosphate, pH=8.83) buffer conditions, each exhibiting different potentials to enhance the infection of HIV in vitro due to different assemble ...


Light Trapping In Thin Film Crystalline Silicon Solar Cells, Javaneh Boroumand Azad Jan 2017

Light Trapping In Thin Film Crystalline Silicon Solar Cells, Javaneh Boroumand Azad

Electronic Theses and Dissertations

This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0°-65°. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains ...


Novel Photonic Resonance Arrangements Using Non-Hermitian Exceptional Points, Hossein Hodaei Jan 2017

Novel Photonic Resonance Arrangements Using Non-Hermitian Exceptional Points, Hossein Hodaei

Electronic Theses and Dissertations

In recent years, non-Hermitian degeneracies also known as exceptional points (EPs) have emerged as a new paradigm for engineering the response of optical systems. EPs can appear in a wide class of open non-Hermitian configurations. Among different types of non-conservative photonic systems, parity-time (PT) symmetric arrangements are of particular interest since they provide an excellent platform to explore the physics of exceptional points. In this work, the intriguing properties of exceptional points are utilized to address two of the long standing challenges in the field of integrated photonics- enforcing single mode lasing in intrinsically multimode cavities and enhancing the sensitivity ...


Spin And Charge Transport In Graphene Based Devices, Marta Anguera Antonana Jan 2017

Spin And Charge Transport In Graphene Based Devices, Marta Anguera Antonana

Electronic Theses and Dissertations

The present dissertation is comprehended in two main parts. The first part is focused on understanding the mechanisms behind spin current to charge current interconversion (i.e. the spin Hall angle), where the spin current is generated by means of spin pumping. The measurement of a positive spin Hall angle of magnitude 0.004 in Uranium is reported in Chapter 2. These results support the idea that the electronic configuration may be at least as important as the atomic number in governing spin Hall effects. In Chapter 3, the design of a spintronics device designed to interconvert charge and spin ...


Predictive Modeling Of Functional Materials For Catalytic And Sensor Applications, Takat Rawal Jan 2017

Predictive Modeling Of Functional Materials For Catalytic And Sensor Applications, Takat Rawal

Electronic Theses and Dissertations

The research conducted in my dissertation focuses on theoretical and computational studies of the electronic and geometrical structures, and the catalytic and optical properties of functional materials in the form of nano-structures, extended surfaces, two-dimensional systems and hybrid structures. The fundamental aspect of my research is to predict nanomaterial properties through ab-initio calculations using methods such as quantum mechanical density functional theory (DFT) and kinetic Monte Carlo simulation, which help rationalize experimental observations, and ultimately lead to the rational design of materials for the electronic and energy-related applications. Focusing on the popular single-layer MoS2, I first show how its hybrid ...


Charge And Spin Transport In Low-Dimensional Materials, Amin Ahmadi Jan 2017

Charge And Spin Transport In Low-Dimensional Materials, Amin Ahmadi

Electronic Theses and Dissertations

My research has been focused on two main areas. First, electronic transports in chiral carbon nanotubes in the presence of charged adatoms. To study such systems we employed recursive Greens function technique to evaluate the conductance using the Landauer formula. Comparing with the experimental data, we determined the effective amplitude and the range of scattering potentials. In addition, using a similar approach we explained qualitatively an unusual conductance feature in a metallic carbon nanotube. The second part of my study was concerned to the dynamical spin injection and spin currents in low-dimensional materials. We have developed an atomistic model to ...


Mesoscopic Interactions In Complex Photonic Media, Roxana Rezvani Naraghi Jan 2017

Mesoscopic Interactions In Complex Photonic Media, Roxana Rezvani Naraghi

Electronic Theses and Dissertations

Mesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in complex media. In-depth understanding of mesoscale phenomena provides the required quantitative explanations that neither microscopic nor macroscopic models of light-matter interaction can afford. Modeling mesoscopic systems is challenging because ...


The Subject Librarian Newsletter, Physics, Fall 2016, Sandy Avila Dec 2016

The Subject Librarian Newsletter, Physics, Fall 2016, Sandy Avila

Libraries' Newsletters

No abstract provided.


The Subject Librarian Newsletter, Physics, Fall 2016, Patti Mccall Sep 2016

The Subject Librarian Newsletter, Physics, Fall 2016, Patti Mccall

Libraries' Newsletters

No abstract provided.


The Subject Librarian Newsletter, Creol, Spring 2016, Patti Mccall Mar 2016

The Subject Librarian Newsletter, Creol, Spring 2016, Patti Mccall

Libraries' Newsletters

No abstract provided.


The Subject Librarian Newsletter, Physics, Spring 2016, Patti Mccall Mar 2016

The Subject Librarian Newsletter, Physics, Spring 2016, Patti Mccall

Libraries' Newsletters

No abstract provided.


An Improved Tight-Binding Model For Phosphorene, Kursti Delello Jan 2016

An Improved Tight-Binding Model For Phosphorene, Kursti Delello

Honors Undergraduate Theses

The intent of this thesis is to improve upon previously proposed tight-binding models for one dimensional black phosphorus, or phosphorene. Previous models offer only a qualitative analysis of the band structure of phosphorene, and fail to fully realize critical elements in the electronic band structure necessary for transport calculations. In this work we propose an improved tight-binding model for phosphorene by including up to eight nearest-neighbor interactions. The efficacy of the model is verified by comparison with DFT-HSE06 calculations, and the anisotropy of the effective masses in the armchair and zigzag directions is considered.