Abstract

Pulsed laser beam propagation through the atmosphere is described by a model that contains the transient effects of air wave development. This study considers the initial stages in the propagation of a laser beam; the computer calculation follows the process during the time regime in which pressure gradients are important. Energy absorbed by the medium from the beam during a time increment is added to the existing internal energy in the form of excited molecular states. Deactivation rates are specified by pressure, temperature, and component species such as CO₂ and H₂O. Absorption and deactivation processes change the temperature of the air and cause the buildup of the cylindrically symmetric air waves. A Richtmyer-von Neuman finite difference scheme follows the waves’ development, and a pseudoviscosity term is used to smooth steep pressure gradients. During the growth of the related gradients in the index of refraction the equations for power flow in the initially diffraction-limited beam are continually changed to allow for refraction. Power densities in the focal plane are obtained as a function of time, atmospheric constitution, power, beam source aperture diameter, range, and radius from the beam axis in the focal plane.

© 1972 Optical Society of America

Thermal Blooming of Laser Beams in Fluids

John N. Hayes
Appl. Opt. 11(2) 455-461 (1972)

Mutual Coherence Function of a Finite Cross Section Optical Beam Propagating in a Turbulent Medium

H. T. Yura
Appl. Opt. 11(6) 1399-1406 (1972)

Approximate Analyses of the Refractive Attenuation of Laser Beam Intensities by Turbulent Absorbing Media

M. R. Wohlers
Appl. Opt. 11(6) 1389-1398 (1972)

Geometric Optics of Thermal Blooming in Gases. Part 1

P. V. Avizonis, C. B. Hogge, R. R. Butts, and J. R. Kenemuth
Appl. Opt. 11(3) 554-564 (1972)

Effects of the Atmosphere on the Propagation of 10.6-μ Laser Beams

J. N. Hayes, P. B. Ulrich, and A. H. Aitken
Appl. Opt. 11(2) 257-260 (1972)