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open access

A Determination of the Fine Structure Constant Using Precision Measurements of Helium Fine Structure

Description: Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant α. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extr… more
Date: August 2010
Creator: Smiciklas, Marc
open access

Dynamic Screening via Intense Laser Radiation and Its Effects on Bulk and Surface Plasma Dispersion Relations

Description: Recent experimentation with excitation of surface plasmons on a gold film in the Kretschmann configuration have shown what appears to be a superconductive effect. Researchers claimed to see the existence of electron pairing during scattering as well as magnetic field repulsion while twisting the polarization of the laser. In an attempt to explain this, they pointed to a combination of electron-electron scattering in external fields as well as dynamic screening via intense laser radiation. Th… more
Date: August 2017
Creator: Lanier, Steven t
open access

EEG, Alpha Waves and Coherence

Description: This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and non-ergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is … more
Date: May 2010
Creator: Ascolani, Gianluca
open access

Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Description: With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the disser… more
Date: May 2012
Creator: Nagaraj, Nagaraj
open access

Effects of Quantum Coherence and Interference

Description: Quantum coherence and interference (QCI) is a phenomenon that takes place in all multi-level atomic systems interacting with multiple lasers. In this work QCI is used to create several interesting effects like lasing without inversion (LWI), controlling group velocity of light to extreme values, controlling the direction of propagation through non-linear phase matching condition and for controlling the correlations in field fluctuations. Controlling group velocity of light is very interesting b… more
Date: August 2013
Creator: Davuluri, Subrahmanya Bhima Sankar
open access

The Effects of Residual Gases on the Field Emission Properties of ZnO, GaN, ZnS Nanostructures, and the Effects of Light on the Resistivity of Graphene

Description: In this dissertation, I present that at a vacuum of 3×10-7 Torr, residual O2, CO2, H2 and Ar exposure do not significantly degrade the field emission (FE) properties of ZnO nanorods, but N2 exposure significantly does. I propose that this could be due to the dissociation of N2 into atomic nitrogen species and the reaction of such species with ZnO. I also present the effects of O2, CO2, H2O, N2, H2, and Ar residual gas exposure on the FE properties of GaN and ZnS nanostructure. A brief review of… more
Date: May 2014
Creator: Mo, Yudong
open access

Electrical Conduction Mechanisms in the Disordered Material System P-type Hydrogenated Amorphous Silicon

Description: The electrical and optical properties of boron doped hydrogenated amorphous silicon thin films (a-Si) were investigated to determine the effect of boron and hydrogen incorporation on carrier transport. The a-Si thin films were grown by plasma enhanced chemical vapor deposition (PECVD) at various boron concentrations, hydrogen dilutions, and at differing growth temperatures. The temperature dependent conductivity generally follows the hopping conduction model. Above a critical temperature, the d… more
Date: December 2014
Creator: Shrestha, Kiran (Engineer)
open access

Electrically Tunable Absorption and Perfect Absorption Using Aluminum-Doped Zinc Oxide and Graphene Sandwiched in Oxides

Description: Understanding the fundamental physics in light absorption and perfect light absorption is vital for device applications in detector, sensor, solar energy harvesting and imaging. In this research study, a large area fabrication of Al-doped ZnO/Al2O3/graphene/Al2O3/gold/silicon device was enabled by a spin-processable hydrophilic mono-layer graphene oxide. In contrast to the optical properties of noble metals, which cannot be tuned or changed, the permittivity of transparent metal oxides, such a… more
Date: December 2018
Creator: Adewole, Murthada Oladele
open access

An Electro- Magneto-static Field for Confinement of Charged Particle Beams and Plasmas

Description: A system is presented that is capable of confining an ion beam or plasma within a region that is essentially free of applied fields. An Artificially Structured Boundary (ASB) produces a spatially periodic set of magnetic field cusps that provides charged particle confinement. Electrostatic plugging of the magnetic field cusps enhances confinement. An ASB that has a small spatial period, compared to the dimensions of a confined plasma, generates electro- magneto-static fields with a short range.… more
Date: May 2014
Creator: Pacheco, Josè L.
open access

Electromagnetically Modulated Sonic Structures

Description: Phononic crystals are structures composed of periodically arranged scatterers in a background medium that affect the transmission of elastic waves. They have garnered much interest in recent years for their macro-scale properties that can be modulated by the micro-scale components. The elastic properties of the composite materials, the contrast in the elastic properties of the composite materials, and the material arrangement all directly affect how an elastic wave will behave as it propagates … more
Date: May 2014
Creator: Walker, Ezekiel Lee
open access

Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

Description: The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metal-optics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing … more
Date: May 2012
Creator: Gryczynski, Karol Grzegorz
open access

Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Description: III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN… more
Date: May 2012
Creator: Llopis, Antonio
open access

Emergence of Cooperation and Homeodynamics as a Result of Self Organized Temporal Criticality: From Biology to Physics

Description: This dissertation is an attempt at establishing a bridge between biology and physics leading naturally from the field of phase transitions in physics to the cooperative nature of living systems. We show that this aim can be realized by supplementing the current field of evolutionary game theory with a new form of self-organized temporal criticality. In the case of ordinary criticality, the units of a system choosing either cooperation or defection under the influence of the choices done by thei… more
Date: August 2018
Creator: Mahmoodi, Korosh
open access

Enhancements of Mechanical, Thermal Stability, and Tribological Properties by Addition of Functionalized Reduced Graphene Oxide in Epoxy

Description: The effects of octadecylamine-functionalized reduced graphene oxide (FRGO) on the frictional and wear properties of diglycidylether of bisphenol-A (DGEBA) epoxy are studied using a pin-on-disk tribometer. It was observed that the addition of FRGO significantly improves the tribological, mechanical, and thermal properties of epoxy matrix. Graphene oxide (GO) was functionalized with octadecylamine (ODA), and then reduction of oxygen-containing functional groups was carried out using hydrazine mon… more
Date: August 2014
Creator: Shah, Rakesh K.
open access

Examination of Magnetic Plasma Expulsion

Description: Magnetic plasma expulsion uses a magnetic field distortion to redirect incident charged particles around a certain area for the purposes of shielding. Computational studies are carried out and for certain values of magnetic field, magnetic plasma expulsion is found to effectively shield a sizable area. There are however many plasma behaviors and interactions that must be considered. Applications to a new cryogenic antimatter trap design are discussed.
Date: May 2018
Creator: Phillips, Ryan Edward
open access

Exploring Growth Kinematics and Tuning Optical and Electronic Properties of Indium Antimonide Nanowires

Description: This dissertation work is a study of the growth kinematics, synthesis strategies and intrinsic properties of InSb nanowires (NWs). The highlights of this work include a study of the effect of the growth parameters on the composition and crystallinity of NWs. A change in the temperature ramp-up rate as the substrate was heated to reach the NW growth temperature resulted in NWs that were either crystalline or amorphous. The as-grown NWs were found to have very different optical and electrical pro… more
Date: December 2018
Creator: Algarni, Zaina Sluman
open access

Fabrication and Study of the Optical Properties of 3D Photonic Crystals and 2D Graded Photonic Super-Crystals

Description: In this dissertation, I am presenting my research on the fabrication and simulation of the optical properties of 3D photonic crystals and 2D graded photonic super-crystals. The 3D photonic crystals were fabricated using holographic lithography with a single, custom-built reflective optical element (ROE) and single exposure from a visible light laser. Fully 3D photonic crystals with 4-fold, 5- fold, and 6-fold symmetries were fabricated using the flexible, 3D printed ROE. In addition, novel 2D g… more
Date: December 2018
Creator: Lowell, David
open access

Fabrication of Photonic Crystal Templates through Holographic Lithography and Study of their Optical and Plasmonic Properties in Aluminium Doped Zinc Oxide

Description: This dissertation focuses on two aspects of integrating near-infrared plasmonics with electronics with the intent of developing the platform for future photonics. The first aspect focuses on fabrication by introducing and developing a simple, single reflective optical element capable of high–throughput, large scale fabrication of micro- and nano-sized structure templates using holographic lithography. This reflective optical element is then utilized to show proof of concept in fabricating thre… more
Date: August 2017
Creator: George, David Ray
open access

Fractional Calculus and Dynamic Approach to Complexity

Description: Fractional calculus enables the possibility of using real number powers or complex number powers of the differentiation operator. The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation for a fractional trajectory, that being an average over an ensemble of stochastic trajectories. With an ensemble average perspective, the explanation of the behavior of fractional chaotic systems changes dramatically. Before now what ha… more
Date: December 2015
Creator: Beig, Mirza Tanweer Ahmad
open access

High Efficiency High Power Blue Laser by Resonant Doubling in PPKTP

Description: I developed a high power blue laser for use in scientific and technical applications (eg. precision spectroscopy, semiconductor inspection, flow cytometry, etc). It is linearly polarized, single longitudinal and single transverse mode, and a convenient fiber coupled continuous wave (cw) laser source. My technique employs external cavity frequency doubling and provides better power and beam quality than commercially available blue diode lasers. I use a fiber Bragg grating (FBG) stabilized infr… more
Date: August 2011
Creator: Danekar, Koustubh
open access

Highly Efficient Single Frequency Blue Laser Generation by Second Harmonic Generation of Infrared Lasers Using Quasi Phase Matching in Periodically Poled Ferroelectric Crystals

Description: Performance and reliability of solid state laser diodes in the IR region exceeds those in the visible and UV part of the light spectrum. Single frequency visible and UV laser diodes with higher than 500 mW power are not available commercially. However we successfully stabilized a multi-longitudinal mode IR laser to 860 mW single frequency. This means high efficiency harmonic generation using this laser can produce visible and UV laser light not available otherwise. In this study we examined… more
Date: August 2014
Creator: Khademian, Ali
open access

How Cooperative Systems Respond to External Forces

Description: Cooperative interactions permeate through nature, bringing about emergent behavior and complexity. Using a simple cooperative model, I illustrate the mean field dynamics that occur at the critical point of a second order phase transition in the framework of Langevin equations. Through this formalism I discuss the response, both linear and nonlinear, to external forces. Emphasis is placed on how information is transferred from one individual to another in order to facilitate the collective resp… more
Date: May 2014
Creator: Svenkeson, Adam
open access

Interacting complex systems: theory and application to real-world situations

Description: The interest in complex systems has increased exponentially during the past years because it was found helpful in addressing many of today's challenges. The study of the brain, biology, earthquakes, markets and social sciences are only a few examples of the fields that have benefited from the investigation of complex systems. Internet, the increased mobility of people and the raising energy demand are among the factors that brought in contact complex systems that were isolated till a few years … more
Date: August 2017
Creator: Piccinini, Nicola
open access

Interaction of Plasmons and Excitons for Low-Dimension Semiconductors

Description: The effects of surface plasmon for InGaN/GaN multi-quantum wells and ZnO nanoparticles optical linear and nonlinear emission efficiency had been experimentally studied. Due to the critical design for InGaN MQWs with inverted hexagonal pits based on GaN, both contribution of surface plasmon effect and image charge effect at resonant and off resonant frequencies were experimentally and theoretically investigated. With off- resonant condition, the InGaN MQWs emission significantly enhanced by meta… more
Date: December 2014
Creator: Lin, Jie (physicist)
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