Abstract

Previous experimental work by our group¹ has shown that the two-photon excitation of the 6p[1/2,0] state of xenon has a fairly sharp threshold for the onset of amplified spontaneous emission (ASE) from the 6p[1/2,0] state to the excited 6s state. The excitation probability has the expected quadratic dependence on excitation intensity below the ASE threshold but an unexpected linear dependence above threshold. We hypothesize that the reduced excitation probability results from an ac Stark shift/broadening of 6p[1/2,0] state by the ASE field. We have numerically solved the coupled Maxwell-Bloch equations with and without the relevant Stark terms. The ASE threshold predicted by the numerical solutions occurs at an intensity about an order of magnitude higher than the experimental value. Because of uncertainties in some of the experimental parameters this difference is not unreasonable. Solution of the equations without Stark terms gives quadratic excitation dependence above the ASE threshold. Including the Stark terms reduces the dependence to a 1.2 power law. The change to a 1.2 power occurs ~50% above ASE threshold, whereas the experimental change occurs almost right at threshold.

© 1991 Optical Society of America