Two-photon spectroscopy: effects of a resonant intermediate state

Abstract

Discusses the theory of Doppler-free two-photon transitions. The theory is worked out for the case of one arbitrarily strong field and one weak field. The Doppler limit is assumed. These simplifications allow the authors to discuss the experimental manifestations of various parameters. They consider power shifts and broadening the number of resonant peaks and their positions. The general case of an off-resonant intermediate state and the single-frequency case with a resonant intermediate state are discussed. The former is found to lead to a power shift, whereas the latter is unshifted in a certain region. In addition the resonant case gives an enhancement without an appreciable increase in width.