An important systematic and mostly detrimental effect in all optical precision measurements is the so-called light shift, the Stark shift due to the electric field of the light waves. Here it depends not only on the intensities of the two lasers but also on their detuning from the optical resonance, measured in units of the homogeneous optical linewidth. This width, in turn, depends on the buffer gas pressure inside the cesium vapor cell. So for a precision measurement of resonance line positions (this is what all our applications rely on) in general one has to stabilize the laser difference frequency, the absolute laser frequency, and the buffer gas pressure.

We have performed detailed series of experiments in order to search the parameter space for suitable operating points where the light shift does not play a role. In fact, it turns out that the buffer gas not only reduces the linewidth and therefore increases the resolution, but also is the light shift dramatically reduced! We describe this result in a publication.

We have also mesured the dependence of the resonance line position on laser detuning from the optical resonance. Details can be found in this publication and also in this publication and in this one.