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Full-Text Articles in Physics

Size-Effect Of Pd Nanoparticles Supported On Zro2 In The Catalytic Reduction Of No By H2, Young Woo Joh May 2011

Size-Effect Of Pd Nanoparticles Supported On Zro2 In The Catalytic Reduction Of No By H2, Young Woo Joh

HIM 1990-2015

Size-selected Pd nanoparticles were synthesized by the reverse-micelle encapsulation method and deposited on a ZrO2 support for the catalytic NO reduction by H2. All of our samples were found to be highly selective, but a significant size effect was not seen for Pd nanoparticles of between 1.2 nm and 5.5 nm. Ultra-small Pd clusters of less than 1 nm were found to be much less active, and are assumed to be affected by an encapsulation effect of the support. Catalyst activity was comparable to that of literature, and is applicable to H2-SCR research.


High Yield Assembly And Electron Transport Investigation Of Semiconducting-Rich Local-Gated Carbon Nanotube Field Effect Transistors, Kristy Kormondy May 2011

High Yield Assembly And Electron Transport Investigation Of Semiconducting-Rich Local-Gated Carbon Nanotube Field Effect Transistors, Kristy Kormondy

HIM 1990-2015

Single-walled carbon nanotubes (SWNTs) are ideal for use in nanoelectronic devices because of their high current density, mobility and subthreshold swing. However, assembly methods must be developed to reproducibly align all-semiconducting SWNTs at specific locations with individually addressable gates for future integrated circuits. We show high yield assembly of local-gated semiconducting SWNTs assembled via AC-dielectrophoresis (DEP). Using individual local gates and scaling the gate oxide shows faster switching behavior and lower power consumption. The devices were assembled by DEP between prefabricated Pd source and drain electrodes with a thin Al/Al2O3 gate in the middle, and the electrical characteristics were ...


Infrared Emission Spectroscopy Of Hot Carbon Monoxide, Farnood Khalilzadeh Rezaie Jan 2011

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 ...


Low Noise And Low Repetition Rate Semiconductor-Based Mode-Locked Lasers, Dimitrios Mandridis Jan 2011

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 ...


Theoretical Study Of Beam Transformations By Volume Diffraction, Sergiy V. Mokhov Jan 2011

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 ...


Metal Blacks As Scattering Centers To Increase The Efficiency Of Thin Film Solar Cells, Deep R. Panjwani Jan 2011

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 ...


Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino Jan 2011

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 ...


Infrared Phased-Array Antenna-Coupled Tunnel Diodes, Brian Alan Slovick Jan 2011

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 ...


Design, Fabrication, And Testing Of High-Transparency Deep Ultra-Violet Contacts Using Surface Plasmon Coupling In Subwavelength Aluminum Meshes, Clarisse Mazuir Jan 2011

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 ...


Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille Jan 2011

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 ...


Low Noise, Narrow Optical Linewidth Semiconductor-Based Optical Comb Source And Low Noise Rf Signal Generation, Ibrahim Tuna Ozdur Jan 2011

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 ...


Perceptual Image Quality Of Launch Vehicle Imaging Telescopes, Joshua K. Lentz Jan 2011

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 ...


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 Jan 2011

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 ...


Laser Induced Breakdown Spectroscopy For Detection Of Organic Residues Impact Of Ambient Atmosphere And Laser Parameters, Christopher G. Brown Jan 2011

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 ...


Single-Electron Transport Spectroscopy Studies Of Magnetic Molecules And Nanoparticles, Firoze Haque Jan 2011

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 Jan 2011

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 ...


Ultra High Density Spectral Beam Combining By Thermal Tuning Of Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Derrek Drachenberg Jan 2011

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 ...


Computationally Efficient Digital Backward Propagation For Fiber Nonlinearity Compensation, Likai Zhu Jan 2011

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 ...


Intracavity Laser Absorption Spectroscopy Using Quantum Cascade Laser And Fabry-Perot Interferometer, Gautam Medhi Jan 2011

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 ...


Computational Study Of The Near Field Spontaneous Creation Of Photonic States Coupled To Few Level Systems, Sergio Tafur Jan 2011

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 ...


Multilayered Planar Periodic Subwavelength Microstructures For Generating And Detecting Circularly Polarized Thermal Infrared Radiation, Samuel Lanning Wadsworth Jan 2011

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 ...