Abstract

Theoretical evaluation of the effects of absorption of a laser beam at 10.6 μ has been investigated using the techniques of geometric optics. The interaction is nonlinear because the refractive index depends, through the mechanism of absorption, upon the irradiance distribution in the propagating wave. Atmospheric absorption at 10.6 μ is caused by CO₂ and H₂O in the atmosphere. Associated with absorption by CO₂ and transverse flow caused by atmospheric winds or beam motion are vibrational relaxation effects, which can either heat or cool the atmosphere. If the atmosphere is cooled, the beam is self-focused. The velocity-altitude dependences of the heating and cooling regimes are defined. The amount of cooling increases with increasing altitude and decreasing relative humidity. Numerical results for the irradiance distribution in each regime are presented. At low altitudes the initially circular contours of the constant irradiance have been deformed into crescent-shaped contours and the beam has deflected into the wind. At high altitudes where significant cooling has occurred, the contours of constant irradiance are oval shaped with significant enhancement of the peak irradiance.

© 1970 Optical Society of America

Effects of Nonlinear Refraction at 10.6 μm on the Far-Field Irradiance Distribution*

J. Wallace
J. Opt. Soc. Am. 62(3) 373-378 (1972)

Effects of 10.6-μ Laser Induced Air Chemistry on the Atmospheric Refractive Index

A. D. Wood, M. Camac, and E. T. Gerry
Appl. Opt. 10(8) 1877-1884 (1971)

Limitations on the Atmospheric Thermal Effects for High-Power CO₂ Laser Beams*

E. L. Breig
J. Opt. Soc. Am. 62(4) 518-528 (1972)

Compensation for Atmospheric Phase Effects at 10.6 μ

W. T. Cathey, C. L. Hayes, W. C. Davis, and V. F. Pizzurro
Appl. Opt. 9(3) 701-707 (1970)

Absorption Saturation Effects on High-Power CO₂ Laser Beam Transmission

David C. Pridmore-Brown
Appl. Opt. 12(9) 2188-2191 (1973)