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Articles 1 - 23 of 23
Full-Text Articles in Physics
Ultra High Density Spectral Beam Combining By Thermal Tuning Of Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Derrek Drachenberg
Ultra High Density Spectral Beam Combining By Thermal Tuning Of Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Derrek Drachenberg
Electronic Theses and Dissertations
High power lasers with diffraction limited beam quality are desired for many applications in defense and manufacturing. A lot of applications require laser beams at the 100 kW power level along with divergence close to the diffraction limit. The figure of merit for a beam used in such applications should be radiance which determines the laser power delivered to a remote target. One of the primary limiting factors is thermal distortion of a laser beam caused by excessive heat generated in the laser media. Combination of multiple laser beams is usually considered as a method to mitigate these limitations. Spectral …
Theoretical Study Of Beam Transformations By Volume Diffraction, Sergiy V. Mokhov
Theoretical Study Of Beam Transformations By Volume Diffraction, Sergiy V. Mokhov
Electronic Theses and Dissertations
Laser beams can be manipulated by volume diffractive elements in addition to conventional optical elements like mirrors, lenses, and beam splitters. Conventional optical elements can be described by applying the basic laws of reflection and refraction at the surfaces of the elements. Even diffraction by surface gratings utilizes relatively simple mathematics. This is to be contrasted with the volume diffraction, which requires coupled wave theory in the slowly varying envelope approximation (SVEA) to obtain accurate results. Efficient spatially distributed diffraction of laser beams is possible due to the high coherence of laser light, and it occurs at specific resonant Bragg …
High Pressure And Micro-Spectroscopic Studies Of Single Living Erythrocytes And The Intraerythrocytic Multplication Cycle Of Plasmodium Falciparum, Silki Arora
Electronic Theses and Dissertations
A novel experimental approach for micro-absorption spectroscopy and high-pressure microscopy of single cells is developed and applied to the investigation of morphological, volume, and spectroscopic changes in healthy red blood cells (RBCs) and erythrocytes infected with the malaria parasite Plasmodium falciparum. Through real-time optical imaging of individual erythrocytes (size ~ 7[micrometer]) we determine the change in volume over the pressure range from 0.1 to 210 MPa. The lateral diameter of healthy RBCs decreases reversibly with pressure with an approximate slope of 0.015 [micrometer] / MPa. In infected cells, clear differences in the deformability and between the compression and decompression curves …
Characterization Of The Nonlinear Refractive Index Of Carbon Disulfide Over An Extended Spectral And Temporal Range, Marcus Seidel
Characterization Of The Nonlinear Refractive Index Of Carbon Disulfide Over An Extended Spectral And Temporal Range, Marcus Seidel
Electronic Theses and Dissertations
The intensity dependent refractive index change of a medium is frequently described in terms of the product n₂ · I where n₂ is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS₂) however, nuclear motions contribute to n₂. These motions occur on the sub picosecond time scale and thus become especially relevant for ultrashort laser pulses. The neat liquid CS₂ is studied because it exhibits a large nonlinear refractive index in …
An Approach To Improve The Failure Rate Model Of A Solid State Laser By Utalizing The Physics Of Failure Methodology, Omar L. Thompson
An Approach To Improve The Failure Rate Model Of A Solid State Laser By Utalizing The Physics Of Failure Methodology, Omar L. Thompson
Electronic Theses and Dissertations
The ability to predict the failure rate of any military laser is very critical. In-field laser usage does not support the troubleshooting and repairing of a complex electro optical system. The only published laser failure rate model was last updated by the Department of Defense in 1975. Consequently, the failure rate predicted is inaccurate due to model deficiencies. This dissertation has developed a laser failure rate model for diode pumped lasers with improved failure rate prediction accuracy. The model has surpassed the capabilities of the Department of Defense model by the inclusion of key performance attributes that are currently not …
Computational Study Of The Near Field Spontaneous Creation Of Photonic States Coupled To Few Level Systems, Sergio Tafur
Computational Study Of The Near Field Spontaneous Creation Of Photonic States Coupled To Few Level Systems, Sergio Tafur
Electronic Theses and Dissertations
Models of the spontaneous emission and absorption of photons coupled to the electronic states of quantum dots, molecules, N-V (single nitrogen vacancy) centers in diamond, that can be modeled as artificial few level atoms, are important to the development of quantum computers and quantum networks. A quantum source modeled after an effective few level system is strongly dependent on the type and coupling strength the allowed transitions. These selection rules are subject to the Wigner-Eckert theorem which specifies the possible transitions during the spontaneous creation of a photonic state and its subsequent emission. The model presented in this dissertation describes …
Infrared Emission Spectroscopy Of Hot Carbon Monoxide, Farnood Khalilzadeh Rezaie
Infrared Emission Spectroscopy Of Hot Carbon Monoxide, Farnood Khalilzadeh Rezaie
Electronic Theses and Dissertations
Gas giant exoplanets known as hot Jupiters orbit close to their parent stars and are heated to high temperatures. Their infrared spectra, measured by photometry during secondary eclipses, are dominated by carbon monoxide and methane, the principle reservoirs of carbon on these planets. The relative CO and CH4 abundances inform us about temperature and pressure conditions and also about mixing by global winds driven by intense but asymmetric heating for these tidally locked bodies. Emission spectra collected during secondary eclipses, as the hot Jupiter passes behind its parent star, in principle allows a determination of the CO:CH4 concentration ratio. Since …
Perceptual Image Quality Of Launch Vehicle Imaging Telescopes, Joshua K. Lentz
Perceptual Image Quality Of Launch Vehicle Imaging Telescopes, Joshua K. Lentz
Electronic Theses and Dissertations
A large fleet (in the hundreds) of high quality telescopes are used for tracking and imaging of launch vehicles during ascent from Cape Canaveral Air Force Station and Kennedy Space Center. A maintenance tool has been development for use with these telescopes. The tool requires rankings of telescope condition in terms of the ability to generate useful imagery. It is thus a case of ranking telescope conditions on the basis of the perceptual image quality of their imagery. Perceptual image quality metrics that are well-correlated to observer opinions of image quality have been available for several decades. However, these are …
Single-Electron Transport Spectroscopy Studies Of Magnetic Molecules And Nanoparticles, Firoze Haque
Single-Electron Transport Spectroscopy Studies Of Magnetic Molecules And Nanoparticles, Firoze Haque
Electronic Theses and Dissertations
Magnetic nanoparticles and molecules, in particular ferromagnetic noble metal nanoparticles, molecular magnet and single-molecule magnets (SMM), are perfect examples to investigate the role of quantum mechanics at the nanoscale. For example, SMMs are known to reverse their magnetization by quantum tunneling in the absence of thermal excitation and show a number of fundamental quantum mechanical manifestations, such as quantum interference effects. On the other hand, noble metal nanoparticles are found to behave ferromagnetically for diameters below a few nanometers. Some of these manifestations are still intriguing, and novel research approaches are necessary to advance towards a more complete understanding of …
Few-Cycle Pulses Amplification For Attosecond Science Applications Modeling And Experiments, Michael Hemmer
Few-Cycle Pulses Amplification For Attosecond Science Applications Modeling And Experiments, Michael Hemmer
Electronic Theses and Dissertations
The emergence of mode-locked oscillators providing pulses with durations as short as a few electric-field cycles in the near infra-red has paved the way toward electric-field sensitive physics experiments. In addition, the control of the relative phase between the carrier and the pulse envelope, developed in the early 2000’s and rewarded by a Nobel price in 2005, now provides unprecedented control over the pulse behaviour. The amplification of such pulses to the millijoule level has been an on-going task in a few world-class laboratories and has triggered the dawn of attoscience, the science of events happening on an attosecond timescale. …
Design, Fabrication, And Testing Of High-Transparency Deep Ultra-Violet Contacts Using Surface Plasmon Coupling In Subwavelength Aluminum Meshes, Clarisse Mazuir
Design, Fabrication, And Testing Of High-Transparency Deep Ultra-Violet Contacts Using Surface Plasmon Coupling In Subwavelength Aluminum Meshes, Clarisse Mazuir
Electronic Theses and Dissertations
The present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms) transmit less than 50% and 30% respectively at 300 nm. Here we investigate the use of surface plasmons (SPs) to design transparent p-contacts for AlGaN devices …
The Effectiveness Of Teaching Methods Designed To Improve Student Engagement And Retention Of Physics Subject Matter For Both Science And Non-Science Majors, Dan Maronde
Electronic Theses and Dissertations
The necessity of students’ engagement with the subject matter for successful learning is welldocumented in education research in general, and in physics education research in particular. This study examines the merits of two different programs designed to improve student learning through enhanced student engagement with the material. The target populations of the two programs are different: One is the group of students taking a physical science class as part of the general curriculum required of non-science, non-engineering majors; the other is the group of students, mostly in engineering disciplines, who must take the calculus-based introductory physics sequence as part of …
Tunneling Conductance Characterization Of A Quantum Dot In The Fractional Quantum Hall Regime, Douglas E. Willard
Tunneling Conductance Characterization Of A Quantum Dot In The Fractional Quantum Hall Regime, Douglas E. Willard
Electronic Theses and Dissertations
This work represents a first-principles calculation of the electron tunneling current into quantum dots in the fractional quantum Hall effect regime. The system under consideration consists of an idealized Scanning Tunneling Microscope (STM) tip and a quantum dot with disk geometry and interacting electrons in a transverse magnetic field. Within the context of this model the tunneling current between the STM tip and the dot is examined for spin-polarized electrons at and around a filling factor of 1/3. The current expression is based on a second-quantized Hamiltonian in which electrons in the dot are interacting, confined, and restricted to the …
Multilayered Planar Periodic Subwavelength Microstructures For Generating And Detecting Circularly Polarized Thermal Infrared Radiation, Samuel Lanning Wadsworth
Multilayered Planar Periodic Subwavelength Microstructures For Generating And Detecting Circularly Polarized Thermal Infrared Radiation, Samuel Lanning Wadsworth
Electronic Theses and Dissertations
Generation and detection of circularly-polarized (CP) radiation in the 8- to 12-μm band of the infrared (IR) spectrum is crucial for polarization sensing and imaging scenarios. There is very little naturally occurring CP radiation in the long-wave IR band, so that useful functionalities may be obtained by exploiting preferential radiation and transmission characteristics of engineered metamaterials. Conventional CP devices in the IR utilize birefringent crystals, which are typically bulky and expensive to manufacture. The operation of these devices is generally optimized at a single wavelength. Imaging in the long-wave IR is most often broadband, so that achromatic CP-device behavior is …
Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille
Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille
Electronic Theses and Dissertations
The Cassini mission provided wonderful tools to explore Saturn, its satellites and its rings system. The UVIS instrument allowed stellar occultation observations of structures in the rings with the best resolution available (around 10 meters depending on geometry and navigation), bringing our understanding of the physics of the rings to the next level. In particular, we have been able to observe, dissect, model and test the interactions between the satellites and the rings. We first looked at kilometer-wide structures generated by resonances with satellites orbiting outside the main rings. The observation of structures in the C ring and their association …
Intracavity Laser Absorption Spectroscopy Using Quantum Cascade Laser And Fabry-Perot Interferometer, Gautam Medhi
Intracavity Laser Absorption Spectroscopy Using Quantum Cascade Laser And Fabry-Perot Interferometer, Gautam Medhi
Electronic Theses and Dissertations
Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 m) and IR wavelengths (9.38 and 8.1 m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is …
Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino
Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino
Electronic Theses and Dissertations
The effects related to diffraction and interference are ubiquitous in phenomena involving electromagnetic wave propagation, and are accurately predicted and described within the framework of classical electrodynamics. In the vast majority of the cases the qualitative features of the evolution of a propagating wave can be inferred even without detailed calculations. A field distribution will spread upon propagation, will accumulate phase along the direction of power flow, will exert mechanical forces upon scattering objects in the direction of propagation etc. When such predictions fail, counterintuitive effects and new functionalities can be engineered. In this work a series of exceptional cases …
Laser Induced Breakdown Spectroscopy For Detection Of Organic Residues Impact Of Ambient Atmosphere And Laser Parameters, Christopher G. Brown
Laser Induced Breakdown Spectroscopy For Detection Of Organic Residues Impact Of Ambient Atmosphere And Laser Parameters, Christopher G. Brown
Electronic Theses and Dissertations
Laser Induced Breakdown Spectroscopy (LIBS) is showing great potential as an atomic analytical technique. With its ability to rapidly analyze all forms of matter, with little-to-no sample preparation, LIBS has many advantages over conventional atomic emission spectroscopy techniques. With the maturation of the technologies that make LIBS possible, there has been a growing movement to implement LIBS in portable analyzers for field applications. In particular, LIBS has long been considered the front-runner in the drive for stand-off detection of trace deposits of explosives. Thus there is a need for a better understanding of the relevant processes that are responsible for …
Computationally Efficient Digital Backward Propagation For Fiber Nonlinearity Compensation, Likai Zhu
Computationally Efficient Digital Backward Propagation For Fiber Nonlinearity Compensation, Likai Zhu
Electronic Theses and Dissertations
The next generation fiber transmission system is limited by fiber nonlinearity. A distributed nonlinearity compensation method, known as Digital Backward Propagation (DBP), is necessary for effective compensation of the joint effect of dispersion and nonlinearity. However, in order for DBP to be accurate, a large number of steps are usually required for long-haul transmission, resulting in a heavy computational load. In real time DBP implementation, the FIR filters can be used for dispersion compensation and account for most of the computation per step. A method of designing a complementary filter pair is proposed. The individual errors in the frequency response …
Metal Blacks As Scattering Centers To Increase The Efficiency Of Thin Film Solar Cells, Deep R. Panjwani
Metal Blacks As Scattering Centers To Increase The Efficiency Of Thin Film Solar Cells, Deep R. Panjwani
Electronic Theses and Dissertations
Metal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR absorber for bolometric infrared detectors. Gold-black was deposited on commercial thin-film solar cells using a thermal evaporator in a nitrogen ambient at pressures …
Low Noise, Narrow Optical Linewidth Semiconductor-Based Optical Comb Source And Low Noise Rf Signal Generation, Ibrahim Tuna Ozdur
Low Noise, Narrow Optical Linewidth Semiconductor-Based Optical Comb Source And Low Noise Rf Signal Generation, Ibrahim Tuna Ozdur
Electronic Theses and Dissertations
Recently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth from the mode-locked laser, it is critical to know the free spectral range (FSR) of the etalon precisely. First the etalon FSR is measured by using the modified …
Infrared Phased-Array Antenna-Coupled Tunnel Diodes, Brian Alan Slovick
Infrared Phased-Array Antenna-Coupled Tunnel Diodes, Brian Alan Slovick
Electronic Theses and Dissertations
Infrared (IR) dipole antenna-coupled metal-oxide-metal (MOM) tunnel diodes provide a unique detection mechanism that allows for determination of the polarization and wavelength of an optical field. By integrating the MOM diode into a phased-array antenna, the angle of arrival and degree of coherence of received IR radiation can be determined. The angular response characteristics of IR dipole antennas are determined by boundary conditions imposed by the surrounding dielectric or conductive environment on the radiated fields. To explore the influence of the substrate configuration, single dipole antennas are fabricated on both planar and hemispherical lens substrates. Measurements demonstrate that the angular …
Low Noise And Low Repetition Rate Semiconductor-Based Mode-Locked Lasers, Dimitrios Mandridis
Low Noise And Low Repetition Rate Semiconductor-Based Mode-Locked Lasers, Dimitrios Mandridis
Electronic Theses and Dissertations
The topic of this dissertation is the development of low repetition rate and low noise semiconductor-based laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analogto-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated chirped pulse laser sources. Moreover, the focus is shifted to a specific application of the linearly chirped pulses, timestretched photonic analog-to-digital conversion (TS ADC). The challenges of …