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Proceedings Paper

Study Of The Propagation Of A High Power Infrared Laser Beam Through The Atmosphere. Influence Of Meteorological Conditions
Author(s): C. Lefauconnier; M. Autric; P. Vigliano; Ph. Bournot; G. Inglesakis
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Paper Abstract

Propagation through the atmosphere of a high power laser beam is limited by gaseous and particulate extinction and above all by optical breakdown induced by aerosols with relatively low intensity thresholds. The plasma created strongly absorbs the incident laser radiation and thus limits the maximum energies transmitted behind the breakdown zone. The object of this paper is to study breakdown thresholds in terms of energy density and incident intensity as well as transmission ratios of a CO2 laser beam as a function of natural atmospheric conditions. The setting up of an automatic station for meteorological and fine granulometric measurements enabled us to know the state of the atmosphere over the first ten meters of the surface boundary layer at each moment during laser shots. Five kinds of characteristic situation from the meteorological point of view with visibility greater than 5 km was studied : A-cold anticyclone conditions with the approach of an atmospheric disturbance 6-humid low pressure conditions C-disturbed conditions : rain and drizzle D-maritime and continental wind conditions E-breaking wave sea-state simulation with criteria of similarity. The analysis was carried out in two steps. The first consisted in correlating the variations in meterological parameters and those of the granulometry of the atmospheric aerosol. The second step linked the granulometric fluctuations to the variations in break-down threshold and transmission ratios. Intensity and fluence thresholds from 70-90 MW/cm2 ; 2-4 J/cm2 up to 150-160 MW/cm2 ; 6,5-7,5 J/cm2 have been measured for these different conditions. Comparing the best transmission ratios obtained in a cleaned atmosphere with the worst in strongly breaking sea conditions, we have obtained for 62 J/cm2, energy transmission of 90 % and 40 % respectively and 25 % to 15 % for 250 J/cm2.

Paper Details

Date Published: 20 June 1989
PDF: 10 pages
Proc. SPIE 1031, 7th Intl Symp on Gas Flow and Chemical Lasers, (20 June 1989); doi: 10.1117/12.950575
Show Author Affiliations
C. Lefauconnier, Institute of Fluid Mechanics (France)
M. Autric, Institute of Fluid Mechanics (France)
P. Vigliano, Institute of Fluid Mechanics (France)
Ph. Bournot, Institute of Fluid Mechanics (France)
G. Inglesakis, Institute of Fluid Mechanics (France)


Published in SPIE Proceedings Vol. 1031:
7th Intl Symp on Gas Flow and Chemical Lasers

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