Abstract

The problem of a two-level atom interacting with modulated or multifrequency fields has been the subject of much work in magnetic resonance experiments. More recently, experiments dealing with optical interactions have been reported.¹,² Unlike the former, these have been performed in beam experiments to eliminate the effect of Doppler broadening. Here we calculate that Rabi structures, in particular, multiphoton resonances, should be observable even in a gas cell and/or for a broadband source. However, this is true only for fluorescence and absorption at the modulation frequency or harmonics thereof. By contrast, the time-averaged fluorescence, which is the quantity usually studied, becomes structureless on integration over the Doppler profile. The result, which is not consistent with a rate equation analysis, can be qualitatively understood from the resonance behavior of the system. In particular, earlier studies on generalized Bloch-Siegert shifts are extended to harmonic components of the interaction.

© 1988 Optical Society of America