Numerical Modeling of the Propagation of a Laser Pulse Through a Turbulent Atmosphere PDF Download

Author: Benjamin John Redman
Publisher:
ISBN:
Category : Lasers
Languages : en
Pages :

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 56

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This report results from a contract tasking the Institute of Atmospheric Optics, Siberian Branch, as follows: the contractor will investigate theoretically the interaction between femtosecond propagation effects and atmospheric turbulence, supercontinuum emission (spectral broadening), nonlinear scattering by atmospheric aerosols, and theoretical upper and lower limits for nonlinear propagation effects. The specific project objectives are as follows: (1) The theoretical study of powerful femtosecond laser pulse filamentation in the turbulent atmosphere; (2) Researching the supercontinuum cone emission mechanism by numerical simulation of high-power femtosecond laser pulse propagation in the atmosphere; and (3) The theoretical and experimental study of the fundamental problems of scattering of a high-power femtosecond pulse in the atmosphere: nonstationary light scattering in gases and aerosols; nonlinear inelastic nonstationary light scattering by aerosol particles. (26 figures, 73 refs.).

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 76

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In this project, computer simulation and optical modeling of laser beam propagation through the turbulent atmosphere, as well as development of techniques using photorefractive crystals to mitigate phase distortions in laser beams, have been done. In the framework of the first direction the mathematical methods and computational schemes based on split step operators, phase screen model and the Monte Carlo method have been elaborated. Spatial statistics of light field in laser beam has been studied in relation to inner and outer scales for different models of atmospheric turbulence. Regimes of weak, moderate and strong fluctuations have been considered. In the framework of the second direction the possibility of simulation of double pass and anisoplanatic effects by means of few phase screens has been studied. An experimental set up for optical modeling anisoplanatic effects by the use of dynamic phase modulator has been designed. A method of generation of random optical field with variable correlation function has been proposed and tested. In the framework of the third direction the problem of mitigation of distorted optical signals in photorefractive crystals has been studied. An optimal effective operating range of one way system, based on nonlinear interaction of distorted signal with pumping formed by spatial filtering of the signal, has been found. Using the criterion of maximal mitigation of phase and amplitude distortions, the schemes of two and four beam interaction in InP:Fe have been optimized.

Author: Van
Publisher:
ISBN:
Category :
Languages : en
Pages : 17

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We are modeling the propagation of high intensity laser pulses through nonlinear optical materials including interactions of two-photon absorption, excited-state absorption and nonlinear refraction including thermal refraction. We have developed a preliminary code written in C++ applicable to Pentium-based PC's that is currently running and being tested against known results over a large range of input parameters. In particular, this code is being used to model optical limiting devices for sensor protection applications. While agreement is excellent for most nonlinearities at relatively low input energies, at high inputs, where transmittance values can drop to low levels, deviations are observed. It is thought that acoustic effects arising from thermal transients may be responsible. This is currently under investigation. We have recently developed an approximate solution for these photoacoustic nonlinearities that is computationally much faster than our previous code which was so computationally intensive that practical problems were prohibitive. This code is now being tested to verify its range of validity.

Author: Anna Consortini
Publisher:
ISBN:
Category :
Languages : en
Pages : 75

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A large data base of intensity fluctuations of laser radiation through the turbulent atmosphere has been analyzed. The base had been previously obtained in a joint measurement campaign of the Department of Physics, University of Florence, Italy, and the Wave Propagation Laboratory of NOAA/ERL, Boulder, Colorado, U.S.A. It included good quality data collected through continuously evolving atmospheric turbulence, comprising low, moderate and high turbulence levels, as well as structure parameter (the so called structure constant) and inner scale, values, simultaneously measured. Results have been obtained on the four topics of the present contract. (1) The effect of the inner scale of the turbulence on the normalized variance of the intensity (scintillation index) was experimentally demonstrated, for the first time. Plots of intensity variance versus structure parameter, for fixed ranges of the inner scale, allowed an experimental determination of the role played by inner scale and structure parameter. They constitute a reference for comparison with results from theory or numerical simulations. (2) The evolution of the probability distributions with changing propagation conditions was examined. Some comparisons with existing theoretical distributions were made. Necessity for further investigation resulted. (3) A numerical deconvolution procedure was developed, to remove a broad noise from intensity fluctuation histograms, and applied to low intensity data measured with very small apertures. The results were positive (4) Spectral analyses of experimental data as well as time correlations of intensity fluctuations were made. The contribution to scintillation of the high frequency components, related to the wave cohere length, was shown.

Author: Hugo Weichel
Publisher: SPIE Press
ISBN: 9780819404879
Category : Science
Languages : en
Pages : 114

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Author: Larry C. Andrews
Publisher: SPIE-International Society for Optical Engineering
ISBN:
Category : Science
Languages : en
Pages : 820

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Since publication of the first edition of this text in 1998, there have been several new, important developments in the theory of beam wave propagation through a random medium, which have been incorporated into this second edition. Also new to this edition are models for the scintillation index under moderate-to-strong irradiance fluctuations; models for aperture averaging based on ABCD ray matrices; beam wander and its effects on scintillation; theory of partial coherence of the source; models of rough targets for ladar applications; phase fluctuations; analysis of other beam shapes; plus expanded analysis of free-space optical communication systems and imaging systems.

Author: Jan Awrejcewicz
Publisher: BoD – Books on Demand
ISBN: 9533076208
Category : Computers
Languages : en
Pages : 616

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Numerical Simulations of Physical and Engineering Process is an edited book divided into two parts. Part I devoted to Physical Processes contains 14 chapters, whereas Part II titled Engineering Processes has 13 contributions. The book handles the recent research devoted to numerical simulations of physical and engineering systems. It can be treated as a bridge linking various numerical approaches of two closely inter-related branches of science, i.e. physics and engineering. Since the numerical simulations play a key role in both theoretical and application oriented research, professional reference books are highly needed by pure research scientists, applied mathematicians, engineers as well post-graduate students. In other words, it is expected that the book will serve as an effective tool in training the mentioned groups of researchers and beyond.

Author: Larry C. Andrews
Publisher: SPIE-International Society for Optical Engineering
ISBN:
Category : Science
Languages : en
Pages : 506

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Very Good,No Highlights or Markup,all pages are intact.

Author: F. J. Duarte
Publisher: BoD – Books on Demand
ISBN: 9533072423
Category : Technology & Engineering
Languages : en
Pages : 702

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Book Description
In this volume, recent contributions on coherence provide a useful perspective on the diversity of various coherent sources of emission and coherent related phenomena of current interest. These papers provide a preamble for a larger collection of contributions on ultrashort pulse laser generation and ultrashort pulse laser phenomena. Papers on ultrashort pulse phenomena include works on few cycle pulses, high-power generation, propagation in various media, to various applications of current interest. Undoubtedly, Coherence and Ultrashort Pulse Emission offers a rich and practical perspective on this rapidly evolving field.