Heterodyne measurement of parametric dispersion in electromagnetically induced transparency - art. no. 013803

Using three phase-locked lasers, we have observed in a three-level system t he phase shift of the frequency fixed coupling laser in dependence of the p robe laser frequency relative to an off-resonant reference laser. In the vi cinity of the two-photon resonance, the system exhibits electromagnetically induced transparency and we show that the dispersion of coupling and probe field shows different spectra if the probe field frequency is tuned. The p arametric dispersion of the coupling field is measured on a cesium atomic b eam with a heterodyne interferometer over several decades of coupling and p robe laser power. Even with coupling powers in the nW range, the interferom eter gives a good signal-to-noise ratio. The results are in good agreement with a numerical simulation of a semiclassical model. Analytical expression s for the dispersion are given.