Mr. William Nelson Profile

William Nelson

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Publications (6)

Proceedings Article | 7 December 2016 Presentation

Propagation of combined laser beams through atmospheric turbulence (Conference Presentation)

William Nelson, Chensheng Wu, Phillip Sprangle, Christopher Davis

Proceedings Volume 9979, 99790N (2016) https://doi.org/10.1117/12.2239140

KEYWORDS: Fiber lasers, Atmospheric propagation, Atmospheric turbulence, Directed energy weapons, Laser applications, Laser beam propagation, Mode locking, High power lasers, Oscillators, High power fiber amplifiers

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Proceedings Article | 4 September 2015 Paper

Determining beam properties at an inaccessible plane using the reciprocity of atmospheric turbulence

W. Nelson, C. Wu, C. Davis

Proceedings Volume 9614, 96140E (2015) https://doi.org/10.1117/12.2190969

KEYWORDS: Sensors, Receivers, Transmitters, Adaptive optics, Atmospheric propagation, Turbulence, Beam propagation method, Target detection, Modulators, Atmospheric turbulence

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Proceedings Article | 7 October 2014 Paper

Experimental results on the enhanced backscatter phenomenon and its dynamics

Chensheng Wu, William Nelson, Jonathan Ko, Christopher Davis

Proceedings Volume 9224, 922412 (2014) https://doi.org/10.1117/12.2062952

KEYWORDS: Turbulence, Backscatter, Adaptive optics, Cameras, Retroreflectors, Beam splitters, Scintillation, Mirrors, Atmospheric turbulence, Atmospheric propagation

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Proceedings Article | 7 October 2014 Paper

Phase and amplitude wave front sensing and reconstruction with a modified plenoptic camera

Chensheng Wu, Jonathan Ko, William Nelson, Christopher Davis

Proceedings Volume 9224, 92240G (2014) https://doi.org/10.1117/12.2062948

KEYWORDS: Cameras, Reconstruction algorithms, Deformable mirrors, Adaptive optics, Wavefronts, Turbulence, Zernike polynomials, Wavefront sensors, Atmospheric turbulence, Receivers

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Proceedings Article | 7 October 2014 Paper

3D geometric modeling and simulation of laser propagation through turbulence with plenoptic functions

Chensheng Wu, William Nelson, Christopher Davis

Proceedings Volume 9224, 92240O (2014) https://doi.org/10.1117/12.2062945

KEYWORDS: Turbulence, 3D modeling, Atmospheric propagation, Diffraction, Wave propagation, Refractive index, Beam propagation method, 3D displays, Gaussian beams, Atmospheric modeling

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Plenoptic functions are functions that preserve all the necessary light field information of optical events. Theoretical work has demonstrated that geometric based plenoptic functions can serve equally well in the traditional wave propagation equation known as the “scalar stochastic Helmholtz equation”. However, in addressing problems of 3D turbulence simulation, the dominant methods using phase screen models have limitations both in explaining the choice of parameters (on the transverse plane) in real-world measurements, and finding proper correlations between neighboring phase screens (the Markov assumption breaks down). Though possible corrections to phase screen models are still promising, the equivalent geometric approach based on plenoptic functions begins to show some advantages. In fact, in these geometric approaches, a continuous wave problem is reduced to discrete trajectories of rays. This allows for convenience in parallel computing and guarantees conservation of energy. Besides the pairwise independence of simulated rays, the assigned refractive index grids can be directly tested by temperature measurements with tiny thermoprobes combined with other parameters such as humidity level and wind speed. Furthermore, without loss of generality one can break the causal chain in phase screen models by defining regional refractive centers to allow rays that are less affected to propagate through directly. As a result, our work shows that the 3D geometric approach serves as an efficient and accurate method in assessing relevant turbulence problems with inputs of several environmental measurements and reasonable guesses (such as C_n ² levels). This approach will facilitate analysis and possible corrections in lateral wave propagation problems, such as image de-blurring, prediction of laser propagation over long ranges, and improvement of free space optic communication systems. In this paper, the plenoptic function model and relevant parallel algorithm computing will be presented, and its primary results and applications are demonstrated.

Proceedings Article | 7 October 2014 Paper

Enhanced backscatter of optical beams reflected in atmospheric turbulence

W. Nelson, J. Palastro, C. Wu, C. Davis

Proceedings Volume 9224, 922411 (2014) https://doi.org/10.1117/12.2062946

KEYWORDS: Turbulence, Sensors, Atmospheric propagation, Transmitters, Mirrors, Receivers, Reflectors, Retroreflectors, Refractive index, Beam propagation method

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