To formulate a description of nonlinear polarization spectroscopy that is valid over a wide range of pump intensities, we present an approach that considers any order of the external fields. The Liouville von Neumann equation governing the dynamics of a multilevel molecular system is made tractable by expansion of the particular density matrix into powers of the carrier waves of the external fields. For a two-level system a solution of the resulting set of equations to first order of the probe field but to all orders of pump field is demonstrated. A remarkable change in the homogeneously broadened line shape is obtained at high pump intensities, caused by the optical Stark effect among others. Improvements over results derived by other authors are discussed.
© 1997 Optical Society of America
[Optical Society of America ]
W. Beenken and V. May, "Strong-field theory of nonlinear polarization spectroscopy. Fundamentals and the two-level system," J. Opt. Soc. Am. B 14, 2804-2810 (1997)