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Electrical and Computer Engineering Faculty Publications and Presentations

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Articles 631 - 660 of 724

Full-Text Articles in Electrical and Computer Engineering

Field Solutions For Bidirectional High-Gain Laser Amplifiers And Oscillators, Lee W. Casperson, Mohammad Azadeh Mar 1998

Field Solutions For Bidirectional High-Gain Laser Amplifiers And Oscillators, Lee W. Casperson, Mohammad Azadeh

Electrical and Computer Engineering Faculty Publications and Presentations

General analytical solutions are obtained for the amplitude, phase, and intensity of the electromagnetic waves in bidirectional homogeneously broadened high-gain laser amplifiers and oscillators. These solutions are important as increasingly high-gain lasers are being employed in practical systems. Expressions are derived relating the output power to the input, including the effects of arbitrary mirror reflectivities and frequency detunings from the line center. For negligible reflectivities, these regenerative amplifier results reduce to earlier expressions for single-pass high-gain amplifiers. Multivalued outputs also occur, and in the limit of low gain per pass the results are consistent with earlier studies of single-frequency laser …

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Few-Cycle Pulses In Two-Level Media, Lee W. Casperson Jan 1998

Few-Cycle Pulses In Two-Level Media, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Techniques for producing, measuring, and applying ever shorter electromagnetic pulses are being developed for incorporation in a variety of modern high-speed systems. In many cases these pulses are at most a few cycles in length, and so-called half-cycle electromagnetic pulses are also widely employed. The interaction of such pulses with two-level media is considered here in detail, and these media are basic to many of the absorbing and amplifying configurations of optics and laser studies. Significant delays and distortion of the resulting polarization and population pulses can occur, and nonlinear optical effects are also revealed. The limitations of the parity, …

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Exact Graph Coloring For Functional Decomposition: Do We Need It?, Marek Perkowski, Rahul Malvi, Lech Jozwiak Jan 1998

Exact Graph Coloring For Functional Decomposition: Do We Need It?, Marek Perkowski, Rahul Malvi, Lech Jozwiak

Electrical and Computer Engineering Faculty Publications and Presentations

Finding column multiplicity index is one of important component processes in functional decomposition of discrete functions for circuit design and especially Data Mining applications. How important it is to solve this problem exactly from the point of view of the minimum complexity of decomposition, and related to it error in Machine Learning type of applications? In order to investigate this problem we wrote two graph coloring programs: exact program EXOC and approximate program DOM (DOM cab give provably exact results on some types of graphs). These programs were next incorporated into the multi-valued decomposer of functions and relations NVGUD. Extensive …

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Multi-Level Programmable Arrays For Sub-Micron Technology Based On Symmetries, Marek Perkowski, Malgorzata Chrzanowska-Jeske, Yang Xu Jan 1998

Multi-Level Programmable Arrays For Sub-Micron Technology Based On Symmetries, Marek Perkowski, Malgorzata Chrzanowska-Jeske, Yang Xu

Electrical and Computer Engineering Faculty Publications and Presentations

Regular layout is a fundamental concept in VLSI design which can have application in custom design for submicron technologies, designing new architectures for fine-grain Field Programmable Gate Arrays (FPGAs) and Electrically Programmable logic Devices (EPLDs), and minimization of logic functions for existing FPGAs. PLAs are well known examples of regular layouts. Lattice diagrams are another type of regular layouts that have been recently introduced for layout-driven logic synthesis. In this paper we extend and combine theses two ideas, by introducing the multi-level PLA-like structures, composed from multi-output (pseudo) symmetrical lattice planes and other planes (multi-input, multi-output regular blocks). The main …

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Sinusoidal-Gaussian Beams In Complex Optical Systems, Lee W. Casperson, Dennis G. Hall, Anthony A. Tovar Dec 1997

Sinusoidal-Gaussian Beams In Complex Optical Systems, Lee W. Casperson, Dennis G. Hall, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

Sinusoidal-Gaussian beam solutions are derived for the propagation of electromagnetic waves in free space and in media having at most quadratic transverse variations of the index of refraction and the gain or loss. The resulting expressions are also valid for propagation through other real and complex lens elements and systems that can be represented in terms of complex beam matrices. The solutions are in the form of sinusoidal functions of complex argument times a conventional Gaussian beam factor. In the limit of large Gaussian beam size, the sine and cosine factors of the beams are dominant and reduce to the …

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Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl Dec 1997

Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl

Electrical and Computer Engineering Faculty Publications and Presentations

The collapse of laser-induced cavitation bubbles creates acoustic transients within the surrounding medium and also pressure impulses to the ablation target and light-delivery fiber during microsecond laser ablation. The impulses are investigated here with time-resolved flash photography, and they are found to occur whether or not the light-delivery fiber is in contact with the target. We demonstrate that the impulses depend primarily on the energy stored in the cavitation bubble. They are not directly dependent on the mode of light delivery (contact versus noncontact), and they are also not directly correlated to the other acoustic transients. The pressure impulses do …

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Waterfall Lasers, Lee W. Casperson Nov 1997

Waterfall Lasers, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Laser concepts can be applied to a broad range of physical phenomena. One of the closest parallels occurs with the fluttering oscillations that are sometimes observed in the falling sheets of water associated with fountains, dams, and natural waterfalls. In many respects these fluid feedback oscillations are similar to the electromagnetic modes of typical lasers, and recognition of this similarity led to the interpretation of the waterfall behavior. Gain profiles for the waterfall oscillations are developed, and the relationship of experimental waterfall data to the laser-like models is considered in detail.

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Rate-Equation Approximations In High-Gain Lasers, Lee W. Casperson Apr 1997

Rate-Equation Approximations In High-Gain Lasers, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The rate-equation approximation is one of the most fundamental and universally employed simplifications in laser analyses. The accuracy and regions of applicability of this approximation are explored in comparisons with more rigorous semiclassical models. Higher-order rate-equation approximations are also developed, and these improved models can yield much better accuracy than conventional rate equations with little added complexity. The modified adiabatic elimination methods reported here would also be useful in reducing the mathematical models governing other physical systems.

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Generalized Beam Matrices. Iv. Optical System Design, Anthony A. Tovar, Lee W. Casperson Apr 1997

Generalized Beam Matrices. Iv. Optical System Design, Anthony A. Tovar, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Systematic procedures are presented for determining the optical components needed to produce an arbitrary transformation of a Gaussian light beams's spot size, radius of curvature, displacement, and direction of propagation. As an example, an optical system is considered that spatially separates the two coincident Gaussian beams produced by a high-diffraction-loss resonator that uses a Gaussian variable-reflectivity output coupler. In addition, an ABCDGH reverse matrix theorem and an ABCDGH Sylvester theorem are also derived. These matrix theorems may be used to satisfy special constraints inherent in the design of multipass and periodic optical systems.

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Dominant Wave Directions And Significant Wave Heights From Synthetic Aperture Radar Imagery Of The Ocean, Lisa M. Zurk, William J. Plant Feb 1997

Dominant Wave Directions And Significant Wave Heights From Synthetic Aperture Radar Imagery Of The Ocean, Lisa M. Zurk, William J. Plant

Electrical and Computer Engineering Faculty Publications and Presentations

We show that quasi-linear theory accounts for dominant wave directions observed in synthetic aperture radar (SAR) imagery of the ocean for range-to-velocity (R/V) ratios up to 70 s. We also show that when used in combination with Alpers and Hasselmann's [1982] model of signal-to-noise ratios in SAR imagery, this theory yields significant wave heights in good agreement with those actually observed. We have found that the apparent dominant wave direction in SAR imagery taken at a 45° incidence angle can differ from the true wave direction by as much as 40° under certain conditions. To understand such differences, we simulated …

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New Objective Classification System For Nuclear Opacification, Donald D. Duncan, O. B. Shukla, Sheila West, Oliver D. Schein Jan 1997

New Objective Classification System For Nuclear Opacification, Donald D. Duncan, O. B. Shukla, Sheila West, Oliver D. Schein

Electrical and Computer Engineering Faculty Publications and Presentations

We have developed an autonomous objective classification scheme for degree of nuclear opacification. The algorithm was developed by using a series of color 35-mm slides acquired with a Topcon photo slit-lamp microscope and use of standard camera settings. The photographs were digitized, and first, and second-order gray-level statistics were extracted from within circular regions of the nucleus. Classifications of severity were performed by using these features as input to a neural network. Training versus classification performance was tested by using photographs of different eyes, and test/retest classification reproducibility was evaluated by using paired photographs of the same eyes. We demonstrate …

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Generalized Beam Matrices. Iii. Application To Diffraction Analysis, Lee W. Casperson, Anthony A. Tovar Nov 1996

Generalized Beam Matrices. Iii. Application To Diffraction Analysis, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

In analogy with Huygen’s wavelets a new method based on Gaussian beamlets is used to develop a conventional diffraction integral formalism for paraxial optical systems representable by complex 2×2 ABCD Gaussian beam matrices. This method, along with a new phase parameter transformation, is then used to produce a new diffraction integral for studying the propagation of light beams with arbitrary spatial profiles through much more general misaligned complex optical systems representable by 3×3 ABCDGH beam matrices.

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Scattering Properties Of Dense Media From Monte Carlo Simulations With Application To Active Remote Sensing Of Snow, Lisa M. Zurk, L. Tsang, Dale P. Winebrenner Jul 1996

Scattering Properties Of Dense Media From Monte Carlo Simulations With Application To Active Remote Sensing Of Snow, Lisa M. Zurk, L. Tsang, Dale P. Winebrenner

Electrical and Computer Engineering Faculty Publications and Presentations

Monte Carlo simulations are used to derive the phase matrix, effective permittivity, and scattering coefficient for a random medium consisting of densely packed spheres up to 5000 in number. The results include correlated scattering and coherent wave interaction among the scatterers. The Monte Carlo simulations are based on a multiple-scattering formulation of the Foldy-Lax equations. It is shown that the derived phase matrix is in good agreement with dense media radiative transfer theory for copolarized scattering. The depolarization, however, can be substantially larger than conventional theory. Two methods are used to analyze the behavior of the coherent wave to obtain …

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Drug Delivery With Microsecond Laser Pulses Into Gelatin, Hanqun Shangguan, Lee W. Casperson, Alan Shearin, Kenton W. Gregory, Scott A. Prahl Jul 1996

Drug Delivery With Microsecond Laser Pulses Into Gelatin, Hanqun Shangguan, Lee W. Casperson, Alan Shearin, Kenton W. Gregory, Scott A. Prahl

Electrical and Computer Engineering Faculty Publications and Presentations

Photo acoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial …

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Generalized Beam Matrices. Ii. Mode Selection In Lasers And Periodic Misaligned Complex Optical Systems, Lee W. Casperson, Anthony A. Tovar Jan 1996

Generalized Beam Matrices. Ii. Mode Selection In Lasers And Periodic Misaligned Complex Optical Systems, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

A generalized beam matrix method is used to investigate the mode structure of astigmatic misaligned optical systems with loss or gain. In these optical systems the usual real-argument polynomial-Gaussian beams are not eigenfunctions, and off-axis complex-argument polynomial beams must be used. New beam transformations for these complex-argument modes are reported. Stability criteria are developed, and mode selection in laser resonators that contain tilted, displaced, or curved complex optical elements is discussed.

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Fluttering Fountains: Annular Geometry, Lee W. Casperson Sep 1995

Fluttering Fountains: Annular Geometry, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Under certain conditions of flow rate, height, and feedback, periodic or chaotic fluttering oscillations can be observed as the sheet of water from a dam or waterfall fountain descends through the air. Numerical and analytical interpretations of this phenomenon have recently been reported. The extension of these results to other fountain geometries is discussed here together with experimental observations on an annular waterfall fountain.

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Monte Carlo Simulations Of The Extinction Rate Of Densely Packed Spheres With Clustered And Nonclustered Geometries, Lisa M. Zurk, L. Tsang, K. H. Ding, Dale P. Winebrenner Aug 1995

Monte Carlo Simulations Of The Extinction Rate Of Densely Packed Spheres With Clustered And Nonclustered Geometries, Lisa M. Zurk, L. Tsang, K. H. Ding, Dale P. Winebrenner

Electrical and Computer Engineering Faculty Publications and Presentations

Scattering and absorption coefficients are presented from Monte Carlo simulations of electromagnetic wave propagation in a volume of densely packed, random dielectric, absorptive spheres. The particles are modeled both with and without a surface adhesion that causes them to form clustered groups. Results for scatterer densities greater than a few percent by volume differ significantly from those obtained under the independentscattering assumption. The extinction rates agree well with analytic dense-medium theory. Results also show that, on account of local fields experienced by the particles, the system absorption is different from that predicted with an assumption of independent absorption. Scattering is …

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Generalized Beam Matrices: Gaussian Beam Propagation In Misaligned Complex Optical Systems, Anthony A. Tovar, Lee W. Casperson Jul 1995

Generalized Beam Matrices: Gaussian Beam Propagation In Misaligned Complex Optical Systems, Anthony A. Tovar, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

A novel 3 × 3 transfer-matrix method is developed to propagate off-axis Gaussian beams in astigmatic optical systems that may include tilted, displaced, or curved optical elements. Unlike in a previous generalized ray matrix formalism, optical elements that possess gain or loss such as Gaussian apertures, complex lenslike media, and amplifiers are included; and a new beam transformation is found. In addition, a novel exponential variable-reflectivity mirror, which displaces a Gaussian beam without changing its spot size, and a complex prismlike medium are introduced.

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Generalized Sylvester Theorems For Periodic Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar Mar 1995

Generalized Sylvester Theorems For Periodic Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

Sylvester's theorem is often applied to problems involving light propagation through periodic optical systems represented by unimodular 2 × 2 transfer matrices. We extend this theorem to apply to broader classes of optics-related matrices. These matrices may be 2 × 2 or take on an important augmented 3 × 3 form. The results, which are summarized in tabular form, are useful for the analysis and the synthesis of a variety of optical systems, such as those that contain periodic distributed-feedback lasers, lossy birefringent filters, periodic pulse compressors, and misaligned lenses and mirrors. The results are also applicable to other types …

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Dirac's Equation In Semiclassical Physics, Lee W. Casperson Feb 1995

Dirac's Equation In Semiclassical Physics, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Dirac's equation provides the most rigorous basis known for many calculations in relativistic quantum mechanics. A set of dynamical equations having greater intuitive content can be derived from Dirac's equation without any approximations. These secondary equations govern the properties of a Dirac particle as functions of time and space and are similar to the corresponding equations governing a classical charged fluid. Several new density functions are implied by these equations and are appropriate for incorporation into the various semiclassical models of physics.

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Beam Propagation In Parabolically Tapered Graded-Index Waveguides, Anthony A. Tovar, Lee W. Casperson Nov 1994

Beam Propagation In Parabolically Tapered Graded-Index Waveguides, Anthony A. Tovar, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

To a good approximation, the electromagnetic-propagation characteristics of graded-index waveguides can be written in terms of polynomial-Gaussian modes. For uniform quadratic-index waveguides the behavior of these modes is well known. However, there are sometimes practical reasons for using tapered waveguides, but detailed propagation solutions are known for only a few specific taper functions. The parabolic taper is perhaps the most important special case, and the solution-generating techniques that we generalize are used to obtain analytic solutions for this case.

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Generalized Reverse Theorems For Multipass Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar Oct 1994

Generalized Reverse Theorems For Multipass Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

The reverse theorem that governs backward propagation through optical systems represented by transfer matrices is examined for various matrix theories. We extend several reverse theorems to allow for optical systems represented by matrices that may or may not be unimodular and that may be 2 × 2 or take on an augmented 3 × 3 form. As an example, we use the 3 × 3 form of the reverse theorem to study a laser with intracavity misaligned optics. It is shown that, by tilting one of the laser's mirrors, we can align the laser output arbitrarily, and the mirror tilt …

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Fluttering Fountains: Stability Criteria, Lee W. Casperson May 1994

Fluttering Fountains: Stability Criteria, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The fluttering oscillations that have long been seen in falling sheets of water have recently been subjected to detailed theoretical analysis. In this study stability criteria for these oscillations are derived and discussed. These criteria provide insight into the physical mechanisms of the instability and may be employed in the design of fluttering waterfall systems.

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Threshold Characteristics Of Multimode Semiconductor Lasers, Lee W. Casperson, Mehdi Khoshnevissan Jan 1994

Threshold Characteristics Of Multimode Semiconductor Lasers, Lee W. Casperson, Mehdi Khoshnevissan

Electrical and Computer Engineering Faculty Publications and Presentations

The effects of spontaneous emission on the threshold characteristics of multimode laser oscillators with mixed line broadening are considered in detail. Most previous studies of multimode laser operation have emphasized the two limits of homogeneous and inhomogeneous broadening. With homogeneous broadening there is a tendency for oscillation in a single longitudinal mode, while in the inhomogeneous limit oscillation over much of the gain spectrum is expected. All practical lasers are somewhere between these limits, and this study explores the mode characteristics of lasers with mixed line broadening. Special attention is given to the important practical case of semiconductor diode lasers, …

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Transform Method Of Processing For Speckle Strain-Rate Measurements, Donald D. Duncan, Sean J. Kirkpatrick, F. Fausten Mark, Lawrence W. Hunter Jan 1994

Transform Method Of Processing For Speckle Strain-Rate Measurements, Donald D. Duncan, Sean J. Kirkpatrick, F. Fausten Mark, Lawrence W. Hunter

Electrical and Computer Engineering Faculty Publications and Presentations

We have developed a highly sensitive method for measuring thermal expansion, mechanical strain, and creep rates. We use the well-known technique of observing laser speckle with a pair of linear array cameras, but we employ a data-processing approach based on a two-dimensional transform of the speckle histories from each camera. This technique can effect large gauge sizes, which are important in the assessment of the spatial statistics of creep. Further, the algorithm provides simultaneous global estimates of the strain rates at both small- and large-scale sizes. This feature may be of value in the investigation of materials with different short- …

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Programmable Analog Array Circuit, Marek Perkowski, Edmund Pierzchala Jan 1994

Programmable Analog Array Circuit, Marek Perkowski, Edmund Pierzchala

Electrical and Computer Engineering Faculty Publications and Presentations

There is disclosed a programmable analog or mixed analog/ digital circuit. More particularly, this invention provides a circuit architecture that is ?exible for a programmable electronic hardWare device or for an analog circuit Whose input and output signals are analog or multi-valued in nature, and primarily continuous in time. There is further disclosed a design for a current-mode integrator and sample-and-hold circuit, based upon Miller effect.

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Fluttering Fountains: Simplified Models, Lee W. Casperson Oct 1993

Fluttering Fountains: Simplified Models, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Fluttering oscillations are sometimes observed in the falling sheets of water associated with dams and waterfall fountains, and a theoretical simulation of this phenomenon was recently reported. In this study approximate analytical solutions of the previous model are described and compared with the experimental and theoretical observations.

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Scattering Of A Light Beam From Waves At An Air-Sea Interface, Donald D. Duncan, W. H. Carter Jun 1993

Scattering Of A Light Beam From Waves At An Air-Sea Interface, Donald D. Duncan, W. H. Carter

Electrical and Computer Engineering Faculty Publications and Presentations

The authors report a new theory that describes the scattering of an upward propagating laser beam from the sea through the air-sea interface in the presence of sea waves. The sea is assumed to be a uniform dielectric and conventional scattering theory is employed by using a modification to the first Born approximation that permits treatment of surface refraction phenomena. Methods of statistical radiometry are also used in a new manner by assuming that the surface scattering function for the sea waves can be treated by a quasi-homogeneous source model to calculate the second-order correlation functions for the partially coherent …

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Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Stability Criteria For Homogeneous Broadening, Pitak Chenkosol, Lee W. Casperson May 1993

Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Stability Criteria For Homogeneous Broadening, Pitak Chenkosol, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The stability criteria for single-mode standing-wave laser oscillators in the homogeneously broadened limit are reported, and two types of criteria are distinguished. The first type (type 1) corresponds to the minimum value of the threshold parameter for which an infinitesimal perturbation away from steady state grows into an oscillatory solution. A second type (type 2) corresponds to the minimum value of threshold parameter for which large-amplitude oscillations do not decay to the steady-state solution. Undamped pulsations in single-mode homogeneously broadened standing-wave laser oscillators are found to occur at a much higher excitation level than in ring-laser oscillators with homogeneous broadening. …

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Pump And Signal Cross Saturation In Cw Dye Lasers, Lee W. Casperson, A. C. Wilson, W. J. Sandle Jan 1993

Pump And Signal Cross Saturation In Cw Dye Lasers, Lee W. Casperson, A. C. Wilson, W. J. Sandle

Electrical and Computer Engineering Faculty Publications and Presentations

It is well known that the signal output intensity from a dye laser oscillator depends directly on the pump intensity. The opposite effect, the dependence of the transmitted pump intensity on the signal intensity, is studied in detail. The theoretical results are compared with experimental data obtained using an argon‐laser‐pumped rhodamine 6G dye laser.

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