We have reexamined the propagation of a Gaussian beam through a saturable material and derived an expression that exhibits a departure from Beer's law. The results cannot be represented by a generalization of Beer's law in which the absorption coefficient is intensity dependent. We have measured the absorption of the 3.39-μm He–Ne line in methane and found that some of the discrepancies in the literature can be attributed to the neglect of saturation. Theoretical and experimental results are in quantitative agreement.
© 1988 Optical Society of America
R. E. Mueller and A. D. May, "Propagation of a saturating laser beam through methane," J. Opt. Soc. Am. B 5, 112-115 (1988)