The forward and backward waves in a standing-wave laser resonator are coupled by the nonlinear gain. Proper inclusion of interference effects leads to significant changes in intensity relative to the usual approximation.
© 1980 Optical Society of America
G. P. Agrawal and M. Lax, "Effects of interference on gain saturation in laser resonators," J. Opt. Soc. Am. 69, 1717-1719 (1979)