Generalized dressed-atom approach to atom-strong-field interactions—application to the theory of lasers and Bloch-Siegert shifts

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Abstract
A generalized dressed-atom approach (GDAA) is developed to study the interaction of two or more strong fields with atomic and molecular systems. In the GDAA, part of the atom-field interaction is incorporated into the free-atom, free-field Hamiltonian and this expanded Hamiltonian is said to characterize a "dressed atom." The remaining atom-field interaction may then be thought to constitute a probe field interaction for this dressed atom. Provided that the dressed atom constitutes a reasonably good approximation to the true interaction, the GDAA should offer a relatively simple means for semiquantitatively predicting the positions of absorption resonances in quite complex atom-field systems. The GDAA is applied to the theory of a high-intensity, single-mode, standing-wave gas laser, the theory of Bloch-Siegert shifts, and the analysis of Autler-Townes or saturation spectroscopy experiments. The agreement between the GDAA and computer-determined values for laser resonance positions and Bloch-Siegert shifts is found to be surprisingly good over the entire range of applied field strengths. Some methods for using the GDAA to study complex spectroscopic systems are discussed.