Experimental Study of Laser Propagation Through the Atmospheric Turbulence PDF Download
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Author: Kirk Alan Lohnes
Publisher:
ISBN:
Category : Ionosphere
Languages : en
Pages : 198
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Author: Kirk Alan Lohnes
Publisher:
ISBN:
Category : Ionosphere
Languages : en
Pages : 198
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Author: Walter F. Dabberdt
Publisher:
ISBN:
Category : Atmosphere
Languages : en
Pages : 107
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Book Description
Results are presented from an experimental study of laser beam scintillation along a slant path in the atmospheric planetary boundary layer. The primary objective of this research is to determine the influence on eye safety of atmospheric thermal turbulence in causing locally high intensities of energy in laser beams. This work has resulted in the further development of a general eye-hazard evaluation procedure based on atmospheric effects and laser operating conditions. The present work has also resulted in the development of a simple, 'worst-case' guide to estimate the maximum probability of eye damage.
Author: Michael W. Fitzmaurice
Publisher:
ISBN:
Category : Atmospheric chemistry
Languages : en
Pages : 196
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Book Description
The pertinent theoretical background and the results of a group of experiments conducted over 0.4- and 1.17-km near-ground horizontal ranges are presented. (1) The log-amplitude variances for HeNe (0.633 μm) and CO2 (10.6 μm) laser beams were found to have a ratio of 26.8, which is in close agreement with the predictions of Rytov-based spherical-wave theory. (2) Published measurements of the saturation level of the log-amplitude variance are reviewed and several inconsistencies noted. (3) The spatial correlation function of irradiance field was measured and found to agree with theory. The degree of correlation between different frequency beams which had traversed the same optical path was also measured and compared to theory. The data exhibited an unacceptably large scatter and did not show the wavelength dependence. (4) The log-normal, Rayleigh, and Rice probability distributions are discussed in terms of their applicability to irradiance statistics. Relatively weak 10.6 μm irradiance fluctuations were found to be equally well described by the log-normal and Rice distributions; strong fluctuations obtained at 0.488 μm were clearly best described by the log-normal distribution.
Author: Angel Fernandez
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Atmospheric turbulence, generated by a differential temperature between the Earth's surface and the atmosphere, causes effects on optical waves that have been of great interest to scientists for many years. Wave front distortions in the optical wave induced by atmospheric turbulence result in a spreading of the beam beyond that due to pure diffraction, random variations of the position of the beam centroid, and a random redistribution of the beam energy within a cross section of the beam leading to irradiance fluctuations. Those effects have far-reaching consequences on astronomical imaging, free space optics (FSO) communications, remote sensing, laser satellite communication, astronomical imaging, adaptive optics, target designation, hyperspectral LiDAR, and other applications that require the transmission of optical waves through the atmosphere. Throughout this thesis, we introduce a globally concept of turbulence, focusing in atmospheric turbulence.Diverse experiments have been carried out, for instance, the propagation of two parallel thin beams under geometrical optics condition for studying the parameters of optical turbulence, and besides, the same optical configuration was used to investigate the best sampling rate for optical turbulence. Furthermore, we have measured evapotranspiration by remote sensing, in which we have heeded the fluctuations of the refractive index through the intensities of the turbulence. Finally, experiments which involve a new beam are also developed, such as phase-flipped Gaussian beam. This beam shows an experimental reduction on its irradiance fluctuations induced by the turbulence, which means that it has a high performance in optical communications. The experimental reduction aforementioned is proved through the comparison with the theory developed.
Author: J. W. Strohbehn
Publisher: Springer
ISBN: 9783662311615
Category : Technology & Engineering
Languages : en
Pages : 328
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With contributions by numerous experts
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
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: Hugo Weichel
Publisher: SPIE Press
ISBN: 9780819404879
Category : Science
Languages : en
Pages : 114
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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:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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We describe preliminary results of a set of laser beam propagation experiments performed over a long (149 km) near-horizontal propagation path between Mauna Loa (Hawaii Island) and Haleakala (Island of Maui) mountains in February 2010. The distinctive feature of the experimental campaign referred to here as the Coherent Multi-Beam Atmospheric Transceiver (COMBAT) experiments is that the measurements of the atmospheric-turbulence induced laser beam intensity scintillations at the receiver telescope aperture were obtained simultaneously using three laser sources (laser beacons) with different wavelengths. The presented experimental results on intensity scintillation characteristics reveal complexity of the observed phenomena that cannot be fully explained based on the existing atmospheric turbulence models.
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.
