Digital Commons Network^™

Optical Haar Wavelet Transforms Using Computer Generated Holography, Peter G. Block

Theses and Dissertations

This research introduces an optical implementation of the continuous wavelet transform to filter images. The wavelet transform is modeled as a correlation process and is implemented with a Vander Lugt correlator. The orthonormal basis set used is composed of two one-dimensional Haar functions and a two-dimensional Haar function. Each wavelet, as well as its first two dyadic scalings, is implemented with computer generated holography. The Interferogram method, which represents a function only in terms of its phase, is used to encode the wavelet functions. The results are imaged onto a CCD array and captured using a framegrabber. The optical results …

The Effect Of An Adaptive Optical System's Spatio-Temporal Response On Imaging Performance, Patrick M. Harrington

Theses and Dissertations

Ideally, an adaptive optical control system would have instantaneous temporal response and infinite spatial bandwidth. In real systems, the response time of the adaptive optical control system is limited by the integration time of the wave front sensor, the computational time of the control algorithm, and the actuator response time. Additionally, finite inter actuator spacing limits the deformable mirror's ability to reproduce spatial frequencies having a period less than twice this spacing. Although analyses general enough to account for both the temporal and spatial characteristics of the adaptive optical system exist, they are complex and require detailed information regarding the …

Object Tracking Through Adaptive Correlation, Dennis A. Montera

Theses and Dissertations

This paper discusses the use of a correlation based system to track, an object through a series of images based on templates derived from previous image frames. The ability to track is extended to sequences which include multiple objects of interest within the field of view. This is accomplishes by comparing the height and shape of the template autocorrelation to the peaks in the correlation of the template with the next scene. The result is to identify the region in the next scene which best matches the designated target. In addition to correlation plane postprocessing, an adaptive window is used …

A Two-Dimensional Particle Simulation Of Parallel Plate Radio-Frequency (Rf) Glow Discharges, Eric J. Bennett

Theses and Dissertations

A two-dimensional model of parallel plate RF glow discharges was developed to study discharge phenomena important in plasma assisted processing of materials. The particle-in-cell method is used to calculate the trajectories of computer particles under the influence of both self and applied fields. Monte Carlo methods using the null collision technique are used to model collisions between charged particles and neutral gas atoms. Results of computer experiments are presented with special emphasis placed on ion motion in the sheath regions. Experimental results show some qualitative agreement with one-dimensional model results. Further work required to gain quantitative agreement is outlined.

Processability Of Polythiophene Thin Films By Ultraviolet Photo Bleaching, Derek D. Fletcher

Theses and Dissertations

Materials possessing strong ��⁽³⁾ optical properties such as Polythiophene are sought for the production of optical switches. Polythiophene thin films produced by plasma enhanced CVD show a surface rms roughness of 10^-15 angstroms over single square micron areas which is acceptable for wave guiding in the near IR. This research investigates permanently changing the optical properties of such a thin film by exposure to UV radiation (254 nm, 35 mW/cm²), known as photo bleaching, in hope of creating a refractive index boundary for use in total internal reflection. After 60 minutes exposure the refractive index shows …

Cathodoluminescence Spectroscopy Of Zinc Germanium Phosphide Zngep2, Michael R. Gregg

Theses and Dissertations

Zinc Germanium Phosphide (ZnGeP₂) is a nonlinear semiconductor suitable for use as a laser tuning element over the two to six micron wavelength range. Although this crystal has been studied in the past, its luminescent properties are not yet well understood. In this present study, ZnGeP₂ has been examined using cathodoluminescence spectroscopy (CL). Specifically, the spectral dependence of the CL was obtained as a function of electron beam energy, beam current and temperature. The resulting CL was found to be polarized with a peak structure that was dependent on the polarization. This peak structure observed by CL …

Cation Production And Reactions Induced By Electron Impact On Tetraethoxysilane, Jeremy C. Holtgrave

Theses and Dissertations

The production of cations by electron impact on tetraethoxysilane (TEOS) is studied with a Fourier Transform mass spectrometer (FTMS). The operating principles of FTMS are reviewed and the experimental approach to the mass calibration and cross-section measurement is discussed. The cross-sections for total and partial ionization of Si(OC₂H₅)₄ from threshold to 50 eV are measured. Also, the ion chemistry resulting from interactions between ions and neutral TEOS is examined.

Laser Phase Front Measurements Using A Phase Conjugate Twyman-Green Interferometer, William J. Mandeville

Theses and Dissertations

This study demonstrated the use of a phase conjugate TwymanGreen interferometer for measuring the phase fronts of beams emitted by infrared diode lasers operating at 830 nm. This interferometer successfully measured the phase front of a single element diode laser, providing better resolution than its conventional counterpart. The phase conjugate mirror compensated for aberrations introduced by imperfect optics in the phase conjugating arm of the interferometer. This interferometer was unable to measure the phase front of a diode array due to the array's inability to create a phase conjugate return. The array's short coherence length is believed to be the …

Electronic-To-Vibrational (E → V) Energy Transfer From Br* To Co2 And Electronic-To-Vibrational (E → V) Laser Feasibility Studies, Steven M. Katapski

Theses and Dissertations

The energy transfer mechanism from photo-excited bromine atoms (Br(²P_½)) to C0₂ is investigated in a pulsed fluorescence experiment. An excimer-pumped pulsed dye laser operating at 480 nm is used to photolyze molecular bromine, resulting in the creation of one excited state bromine atom, Br(²P_½), and one ground state atom, Br(²P_3/2). The electronically- excited bromine atoms (referred to as Br*) collide with and excite vibrational modes in the ground electronic state of CO₂. Measurements are made of the Br* lifetimes and associated quenching processes, and the …

A Theoretical Study Of The Subband Structures And Tunneling In Polytype Heterostructures, Hong Chen

Theses

A theoretical study of the electronic and optical properties in polytype heterostructures is presented in this thesis.

In the first part of the thesis (Chap. 2 and Chap. 3), an explicit expression for calculating the subband structure and tunneling is formulated by the incorporation of the envelope function approximations and the transfer matrix technique. It is based on the k*p theory as done to date, but contains two significant improvements: a more realistic treatment of the spatial and energetic dependance of effective masses and band edges; the availability of the calculations, in favor of direct numerical evaluation, to various quantum …

Quantitative Measurement Of Pyrolysis And Combustion Species Concentration By Molecular-Beam-Sampling-Mass-Spectrometry, Xian Zhong

Theses

A molecular-beam-sampling apparatus utilizing both a time-of-flight mass spectrometer with vacuum ultraviolet (VUV) photoionization and a quadrupole mass spectrometer with electron impact ionization is described. These systems are used to analyze reactants and products, as well as reactive intermediates, from flow tube experiments at reduced pressures and elevated temperatures. It is shown that the quadrupole signal sensitivity can be predicted using literature cross sections which are based upon the atom hybridization within the various molecules. Measurements of the VUV photoionization sensitivity for stable species led to development of a group additivity approach to predict cross sections. This approach was extended …

Use Of Raman Spectroscopy In Characterizing Soft X-Ray Multilayers: Tools In Understanding Structure And Interfaces, Ming Cai, Qi Wang, David D. Allred, Larry V. Knight, Dorian M. Hatch, A. Reyes-Mena, Guizhong Zhang

Faculty Publications

Our group is studying the structure and interfaces of soft x-ray multilayers by various techniques including x-ray diffraction and Raman spectroscopy. Raman spectroscopy is particularly useful since it is sensitive to the identity of individual bonds and thus can potentially characterize the abruptness of interfaces in multilayers. Blocking interfacial mixing is very important in achieving and maintaining high reflectivity. We report our studies of the as-deposited and postannealed structure of Mo/Si and W/C multilayers. The Mo/Si system is probably the most widely studied multilayer currently because of its potential applications for soft x-ray projection lithography for the range of 13 …

Interaction Of Profiled Light With Contrapropagating Acoustic Waves: Fourier Transform Approach, Partha P. Banerjee, Chen-Wen Tarn, Jaw-Jueh Liu

Electrical and Computer Engineering Faculty Publications

A straightforward Fourier-transform approach is employed to investigate acousto-optic interaction between an input optical beam with arbitrary profile and contrapropagating cw sound in the Bragg regime. The process can be analyzed in terms of the simultaneous scattering of light by the two sound waves in the interaction region. Analytic expressions for the equivalent transfer functions are obtained and the scattered light profiles are plotted.

The Effect Of Contacts On The Performance Of Electron-Beam Controlled Gaas And Diamond Switches, Michael Kevin Kennedy

Electrical & Computer Engineering Theses & Dissertations

The performance of GaAs and diamond as electron-beam controlled closing and opening switches has been studied. An emphasis has been placed on the effect of contacts on the current-voltage characteristics. The two materials studied were GaAs and diamond. Using the same semi-insulating GaAs wafer as a source of material, a bulk device and a p-i-n device have been fabricated and compared. The asymmetry of the pin diode allows operation at higher voltage because of the ability to suppress the lock-on effect. Whereas GaAs was ionized through cathodoluminescence; diamond, in the form of thin films, has been directly ionized by the …

Diffraction In The Binary Encounter Electron Peak Observed In Collisions Of 0.6 Mev Amu⁻¹ I7+, I23+ And Au11+ Projectiles With He And Ar, W. Wolff, J. L. Shinpaugh, H. E. Wolff, Ronald E. Olson, Jee-Ching Wang, S. Lencinas, D. Piscevic, R. Herrmann, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

Relative double differential cross sections for electron emission from collisions of 0.6 MeV amu^-1I⁷⁺and I²³⁺ projectiles with Ar and Au¹¹⁺projectiles with He were measured for electron energies from 100 eV to 2000 eV and for angles from 0° to 50°. Experimentally observed sudden shifts of the position of the binary encounter peak were interpreted as resulting from quantum interference in the scattering of target electrons from the partially stripped projectile ion. To this end calculations for the elastic scattering of free electrons initially at rest in the laboratory reference frame from the screened …

34th Rocky Mountain Conference On Applied Spectroscopy

Rocky Mountain Conference on Magnetic Resonance

Program and registration information for the 34th annual meeting of the Rocky Mountain Conference on Applied Spectroscopy, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 2-6, 1992.

Ultrahigh Vacuum Chamber For Synchrotron X-Ray Diffraction From Films Adsorbed On Single-Crystal Surfaces, John R. Dennison, S. K. Wang, P. Dai, T. Angot, H. Taub, S. N. Ehrlich

All Physics Faculty Publications

An ultrahigh vacuum chamber has been developed for structural analysis of adsorbed films and single‐crystal surfaces using synchrotron x‐ray diffraction. It is particularly well suited for investigations of physisorbed and other weakly bound films. The chamber is small enough to transport and mount directly on a standard four‐axis diffractometer and can also be used independently of the x‐ray diffractometer. A low‐current, pulse‐counting, low‐energy electron diffraction/Auger spectroscopy system with a position‐sensitive detector enables in situ characterization of the film and substrate while the sample is located at the x‐ray scattering position. A closed‐cycle He refrigerator and electron bombardment heater provide controlled …

Traps In Semi-Insulating Inp Studied By Thermally Stimulated Current Spectroscopy, Z. Q. Fang, David C. Look, J. H. Zhao

Physics Faculty Publications

Traps in Fe‐doped semi‐insulating InP samples have been studied by thermally stimulated current spectroscopy with IR (hν≤1.12 eV) excitation at 81 K. The possible involvement of native defects in determining the compensation mechanisms is suggested based on the observation of other than the usual 0.64 eV Fe‐related activation energy for the dark current in one of the four samples supplied from different sources. A metastable behavior of traps in another sample was found and explained by a charge‐controlled defect reaction model. Three out of the six traps observed are suggested to be electron traps and one among the …

Review: 'Theory Of Dielectric Optical Waveguides,' 2nd Edition, By Dietrich Marcuse, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

I suppose I ought to say up front that while preparing this review I often found myself feeling very much like a student evaluating his teacher. After all, it was, in part, the first edition of Dietrich Marcuse's Theory of Dielectric Optical Waveguides (among a handful of other similar texts) from which I first studied the principles of optical waveguide theory under the demanding, yet patient and graceful guidance of Dr. Ahmad Safaai-Jazi. Thus with the utmost respect for a teacher whom I have never met, I shall try to faithfully share my thoughts and feelings regarding the second edition …

Structures Of Selected Boranes And Carboranes, Sunwoo Lee, Peter A. Dowben, A.T. Wen, A.P. Hitchcock, John A. Glass Jr., James T. Spencer

Peter Dowben Publications

Nido-pentaborane(9) (B₅H₉), 1, nido-2,3-diethyl-2,3-dicarbahexaborane(8)[( C₂H₅)₂C₂B₄H₆], 2, nido-decaborane (14) (B₁₀H₁₄), 3, closo- 1,2-dicarbadodecaborane(12) (H₂C₂B₁₀H₁₀), 4, can be used as possible source compounds for boron and boron carbide thin film deposition. Inner shell electron energy-loss spectroscopy (ISEELS) studies of the boron Is and carbon Is core excitations of gas phase species have been undertaken so as to characterize these molecular precursors at solid surfaces. The near edge structure of ISEELS provides a good "fingerprint" …

Analysis Of Multifrequency Dispersive Optical Bistability And Switching In Nonlinear Ring Cavities With Large Medium-Response Times, Pawel Pliszka, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

Using a simple model of a ring cavity comprising a cubically nonlinear medium, we analyze dispersive optical bistability in the presence of more than one spectral component. We show the phenomenon of so-called competition for resonance. In addition to presenting cavity characteristics for the cases of two and three different frequencies, we also discuss the general method for finding steady-state solutions and checking their stability. A simple and efficient algorithm, based on a relaxation method, is devised to find steady-state solutions satisfying appropriate boundary conditions. The relaxation dynamics is physically related to a finite response time of the medium.

Photoluminescence Study Of Si1-XGeX/Si And Si/Ge Strained Layer Superlattices, Todd D. Steiner

Theses and Dissertations

In recent years, there has been interest in obtaining efficient photoluminescence (PL) and electroluminescence from Si_1-xGe_x/Si or Si/Ge superlattices. In this dissertation, longperiod c/Si superlattices grown by molecular beam epitaxy at 500°C and annealed post-growth using rapid thermal annealing were investigated using photoluminescence (PL). The as-grown samples have broad PL bands from isoelectronic centers related to Ge complexes as well as sharp near-edge bound exciton lines. The broad PL band was found to be 120 meV below the band gap, after accounting for the effects of confinement of holes. Post-growth annealing resulted in a reduction in …

Multi-Ion Ambipolar Diffusion, Thomas E. Gist

Theses and Dissertations

The continuity and momentum equations for electrons and multiple ion species are solved analytically and numerically using a new model for ambipolar diffusion. The general form of the model is valid for any quasi-neutral plasma for which the diffusion approximation is appropriate, including positive or negative ions, arbitrary geometries, and time dependence. The model provides criteria for determining when single ion diffusion theory is appropriate for describing multi-ion discharges, when a multi-ion proportional model is appropriate, and when a multi-ion nonproportional model is necessary. An expression is developed which provides a necessary condition for proportionality and provides the proportionality constant …

Experimental Investigation Of Crossflow Instability Waves In Rotating Disk Flow, Alan E. Blanchard

Mechanical & Aerospace Engineering Theses & Dissertations

For the past 40 years, the crossflow (or inflectional) instability associated with rotating disk flow has been generally assumed to be a pure vortex that is fixed with respect to the disk; however, the terms "wave" and "vortex" have also been used interchangeably throughout the computational and experimental literature to describe this instability. Through the use of both hot-wire surveys and smoke-wire flow visualizations in the present investigation, the existence of crossflow instability waves prior to vortex formation has been shown. The results of the hot-wire surveys and smoke-wire flow visualizations for both a "clean" disk case and a disk …

Prediction Of Paper Color: A Process Simulation Approach, Mayank Chaturvedi

Masters Theses

A simulation model was developed for a dye mixing process and for the prediction of the optical properties of the paper. The model was integrated with the MAPPS (Modular Analysis of Pulp and Paper Systems) simulation software package. The model was validated using dyed handsheets made in a laboratory and dyed paper made on a pilot papermachine. Validation comprised of prediction of the optical properties of the handsheets and the machine-made paper which contained various combinations of three non-fluorescent dyes. Sheet reflectances were predicted at 20 nanometer intervals for discrete light wavelength range of 400 to 700 nanometers and verified …

Limaçon Of Pascal Locus Of The Complex Refractive Indices Of Interfaces With Maximally Flat Reflectance-Versus-Angle Curves For Incident Unpolarized Light, R. M.A. Azzam

Electrical Engineering Faculty Publications

For an interface between two isotropic media the power reflectance R_v (ø) is an even function, R_v (ø) = R_v (--), of the angle of incidence ø; hence all the odd derivatives, R_v⁽ⁿ⁾ = dⁿ R_v /døⁿ (n odd), are identically 0 at ø = 0, independent of the incident polarization v. When the incident light is unpolarized (v = u), the second derivative, R_u⁽²⁾, is also 0 at ø = 0, so that the flatness of the R_u -versus-ø curve …

Some Stability Problems In Droplet Formation And Breakup (Report Lstm 351/T/92)., Nihad E. Daidzic

Aviation Department Publications

In this study the instability of droplets and cylindrical jets is investigated. The understanding of these processes has both academic and practical value. Instability of cylindrical jets is theoretically investigated for infinitesimal and finite, but small initial amplitudes (linear and nonlinear stability). For droplets, only linear theory is presented. It is assumed that the capillary force play a dominant role. It is determined that the viscosity exerts a damping effect. In the first section we give an introduction, after which the linear stability theory of cylindrical liquid jets is presented. In the third section the nonlinear jet stability theory is …

Review: 'Optical Fiber Communications' (2nd Edition), By Gerd Keiser, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

If first impressions are worth anything (and they usually are), I would have to admit that my first impression of the second edition of Gerd Keiser's now popular text Optical Fiber Communications was quite good. My compliments are hereby extended to the publisher for choosing a rather handsome cover and dust jacket. It stands in strong contrast to the text's first edition, which still ranks as probably the ugliest book I own, with color choices ranging from dull cream and "baby" blue to pale pink! I am now happy to say that this older version has been discretely·retired to the …

Demonstrating The Utility Of Boron Based Precursor Molecules For Selective Area Deposition In A Scanning Tunneling Microscope, F. Keith Perkins, M. Onellion, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

The scanning tunneling microscope (STM) can be used to selectively deposit material from a gaseous precursor compound. Ultra-small (less than a 100 nm across) spatial dimensions for selective area deposition may be achieved by this means. In this paper we outline a scheme for selecting and designing main group cluster compounds and organometallics for this type of selective area deposition using nido-decaborane(l4) as an example.

Design And Development Of A Superconducting Induction Motor, Terry Bowness

Opportunities for Undergraduate Research Experience Program (OURE)

The discovery of high-T_c superconductors has led to the development of a number of experimental superconducting motors. This report documents the design, construction, and methods of evaluating the performance of an induction motor with a high-T_c superconducting rotor. While others have utilized the Meissner effect, our superconducting motor works due to Lenz’s law. In theory such a device will act as an induction motor only during start-up, after which its behavior is more like that of a synchronous machine. With a one-pole copper squirrel cage providing start-up torque two high-T_c discs encased in the rotor core act …