DOPPLER-FREE MULTI-PHOTON EXCITATION - LIGHT SHIFT AND SATURATION

The influence of the intensity variation of the light in a standing wave on the lineshape of a Doppler-free multi-photon transition is described showing that as long as the light shifts and the saturation are small compared to the Doppler width, a motional narrowing effect occurs and the line remains Lorentzian, the centre being shifted by an amount equal to the mean value of the dynamic Stark effect. The case of transients is also considered showing that at resonance, it is possible to observe different responses according to the light intensity. In particular, it is possible to observe Rabi oscillations only if the Rabi frequency is larger than the natural width and smaller than the Doppler width of the transition.