Accession Number : ADA260712

Title :   Laser Propagation Through Turbulence.

Descriptive Note : Final technical rept. Sep 90-Sep 92,

Corporate Author : FLORENCE UNIV (ITALY) DEPT OF PHYSICS

Personal Author(s) : Consortini, Anna

Report Date : NOV 1992

Pagination or Media Count : 75

Abstract : 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.

Descriptors :   *ATMOSPHERIC MOTION, *LASER BEAMS, *PROPAGATION, APERTURES, ATMOSPHERICS, DATA BASES, DETERMINATION, EXPERIMENTAL DATA, HIGH FREQUENCY, HISTOGRAMS, INDEXES, INTENSITY, ITALY, LOW INTENSITY, OPTICS, PROBABILITY, RADIATION, SCINTILLATION, SIMULATION, THEORY, TURBULENCE, WAVE PROPAGATION.

Subject Categories : Atmospheric Physics
      Lasers and Masers
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE