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
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