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Electrical and Computer Engineering
Electrical and Computer Engineering Faculty Publications and Presentations
- Keyword
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- Gaussian beams (2)
- Lasers (2)
- Bubbles (1)
- Cataract (1)
- Cataract -- Classification (1)
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- Cavitation (1)
- Electromagnetic waves (1)
- Laser ablation (1)
- Lasers -- Analysis (1)
- Lasers -- Mathematical models (1)
- Matrices -- Mathematical models (1)
- Multiphase flow (1)
- Numerical analysis (1)
- Ocean -- Remote sensing (1)
- Oscillations (1)
- Synthetic aperture radar -- Image quality (1)
- Wave guides (1)
Articles 1 - 7 of 7
Full-Text Articles in Engineering
Sinusoidal-Gaussian Beams In Complex Optical Systems, Lee W. Casperson, Dennis G. Hall, Anthony A. Tovar
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 …
Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl
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 …
Waterfall Lasers, Lee W. Casperson
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.
Generalized Beam Matrices. Iv. Optical System Design, Anthony A. Tovar, Lee W. Casperson
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.
Rate-Equation Approximations In High-Gain Lasers, Lee W. Casperson
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.
Dominant Wave Directions And Significant Wave Heights From Synthetic Aperture Radar Imagery Of The Ocean, Lisa M. Zurk, William J. Plant
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 …
New Objective Classification System For Nuclear Opacification, Donald D. Duncan, O. B. Shukla, Sheila West, Oliver D. Schein
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 …