Abstract

A theoretical analysis has been performed of the nonlinear thermal processes associated with the atmospheric absorption of 10.6-μm radiation from laser beams of high power density, with special attention to limitations imposed upon the CO₂ absorption rate by the induced-emission phenomenon. Differential equations relating atmospheric absorption and temperature change are formulated to include this and related high power effects, and are solved numerically for a series of power densities, humidities, and altitudes near sea level. Low power formulas are shown to be unreliable above 10⁴ W/cm², with absorption-saturation processes especially effective in limiting the magnitude of the CO₂ cooling at these large values of the laser power density. Analytic expressions are derived, which provide an accurate description of the temperature profile during the cooling phase. The regions of validity for simplified high and low power approximations to these formulas are also discussed.

© 1972 Optical Society of America

Absorption Saturation Effects on High-Power CO₂ Laser Beam Transmission

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

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 Absorption at 10.6 μ on Laser-Beam Transmission

J. Wallace and M. Camac
J. Opt. Soc. Am. 60(12) 1587-1594 (1970)

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)

Pressure Dependence of Resonance Fluorescence Lifetimes in SF₆ and SF₆–Air Mixtures

M. Garbuny and J. D. Feichtner
Appl. Opt. 11(5) 1019-1024 (1972)