Engineering Commons^™

Alan Turing Se Fraye Un Chemin Jusqu'À La Place De L'Ordinateur, Christof Teuscher

Electrical and Computer Engineering Faculty Publications and Presentations

A brief statement on the significance, impact and future developments related to the work of computer pioneer Alan Turing, in conjunction with Turing Day, held to commemorate his 90th birthday.

*The article is in French

Gain Guiding In Large-Core Bragg Fibers, Xianyu Ao, Tsing-Hua Her, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

We theoretically analyze gain guiding in large-core Bragg fibers, to be used for large-mode-area laser amplifiers with single-transverse-mode operation. The signal is gain-guided in a low-index core, whereas the pump is guided by the photonic bandgap of the Bragg cladding to achieve good confinement. The high-index layers in the Bragg cladding are half-wave thick at the signal wavelength in order to eliminate Bragg reflection, reducing the Bragg fiber effectively to a step-index fiber for gain guiding.

Computer-Aided Assessment Of Diagnostic Images For Epidemiological Research, Alison G. Abraham, Donald D. Duncan, Stephen J. Gange, Sheila West

Electrical and Computer Engineering Faculty Publications and Presentations

Background: Diagnostic images are often assessed for clinical outcomes using subjective methods, which are limited by the skill of the reviewer. Computer-aided diagnosis (CAD) algorithms that assist reviewers in their decisions concerning outcomes have been developed to increase sensitivity and specificity in the clinical setting. However, these systems have not been well utilized in research settings to improve the measurement of clinical endpoints. Reductions in bias through their use could have important implications for etiologic research. Methods: Using the example of cortical cataract detection, we developed an algorithm for assisting a reviewer in evaluating digital images for the presence and …

Effects Of Sea-Surface Conditions On Passive Fathometry And Bottom Characterization, Steven L. Means, Martin Siderius

Electrical and Computer Engineering Faculty Publications and Presentations

Recently, a method has been developed that exploits the correlation properties of the ocean’s ambient noise to measure water depth (a passive fathometer) and seabed layering [M. Sideriuset al., J. Acoust. Soc. Am.120, 1315–1323 (2006)]. This processing is based on the cross-correlation between the surface noise and the echo return from the seabed. To quantitatively study the dependency between processing and environmental factors such as wind speed, measurements were made using a fixed hydrophone array while simultaneously characterizing the environment. The measurements were made in 2006 in the shallow waters (25m)approximately 75km off the coast of Savannah, GA. …

Effects Of Gaussian Fields On The Stability Of Inhomogeneously Broadened Lasers, Pitak Chenkosol, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Under some conditions, spontaneous coherent pulsations are known to occur in the output beams of inhomogeneously broadened laser oscillators. These lasers typically operate with a Gaussian transverse field distribution, while the corresponding theoretical models assume a uniform-plane-wave field. The effects of a Gaussian field on the stability criteria of single-mode inhomogeneously broadened ring laser oscillators are considered in this study. It is found that in comparison to a plane wave a Gaussian field variation still permits low-threshold spontaneous pulsations but reduces the parameter space over which these pulsations can be observed.

Stability Criteria For Spontaneously Pulsing Gas Lasers, Pitak Chenkosol, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Low-threshold spontaneous pulsations are known to occur in the output beams of certain high-gain gas lasers, and good agreement between the experimental observations and numerical models has been achieved. There have also been several analytical studies of threshold criteria for spontaneously pulsing lasers. However, the analytical studies are mostly not applicable to the lasers in which the pulsations have been observed. Stability criteria for high-gain gas lasers are derived in this study, and these criteria are compared with a previously modeled gas laser instability.

Gain Saturation In Gain-Guided Slab Waveguides With Large-Index Antiguiding, Tsing-Hua Her, Xianyu Ao, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

We investigate numerically and analytically the effects of gain saturation on the propagation of the fundamental mode in a gain-guided index-antiguided slab waveguide. The propagating mode adapts to gain saturation by becoming less confined, while at the same time its peak intensity increases more slowly. At steady state, both the mode shape and the power remain constant.

Monte Carlo Green's Function Formalism For The Propagation Of Partially Coherent Light, Scott A. Prahl, David G. Fischer, Donald D. Duncan

Electrical and Computer Engineering Faculty Publications and Presentations

We present a Monte Carlo-derived Green's function for the propagation of partially spatially coherent fields. This Green's function, which is derived by sampling Huygens-Fresnel wavelets, can be used to propagate fields through an optical system and to compute first- and second-order field statistics directly. The concept is illustrated for a cylindrical f/1 imaging system. A Gaussian copula is used to synthesize realizations of a Gaussian Schell-model field in the pupil plane. Physical optics and Monte Carlo predictions are made for the first- and second-order statistics of the field in the vicinity of the focal plane for a variety of source …

Extended Superposed Quantum State Initialization Using Disjoint Prime Implicants, David Rosenbaum, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

Extended Superposed Quantum State Initialization Using Disjoint Prime Implicants (ESQUID) is a new algorithm for generating quantum arrays for the purpose of initializing a desired quantum superposition. The quantum arrays generated by this algorithm almost always use fewer gates than other algorithms and in the worst case use the same number of gates. These improvements are achieved by allowing certain parts of the quantum superposition that cannot be initialized directly by the algorithm to be initialized using special circuits. This allows more terms in the quantum superposition to be initialized at the same time which decreases the number of gates …

Radiative Transfer Theory Applied To Ocean Bottom Modeling, Lisa M. Zurk, Jorge Quijano

Electrical and Computer Engineering Faculty Publications and Presentations

Research on the propagation of acoustic waves in the ocean bottom sediment is of interest for active sonar applications such as target detection and remote sensing. The interaction of acoustic energy with the sea floor sublayers is usually modeled with techniques based on the full solution of the wave equation, which sometimes leads to mathematically intractable problems. An alternative way to model wave propagation in layered media containing random scatterers is the radiative transfer RT formulation, which is a well established technique in the electromagnetics community and is based on the principle of conservation of energy. In this paper, the …