Autler-Townes spectroscopy with interaction-induced dephasing

Abstract

We study the effects of Rydberg-atom interactions on Autler-Townes (AT) spectra in a dense gas of ultracold cesium atoms. The $6{S}_{1/2}$ and $6{P}_{3/2}$ levels of cesium are strongly coupled (Rabi frequency ${\ensuremath{\Omega}}_{c})$, and the resultant AT spectra are probed via excitation into a Rydberg level. Van der Waals interactions between the atoms in the probe Rydberg level give rise to a dephasing rate $({\ensuremath{\gamma}}_{3})$. The interaction-induced dephasing is found to cause characteristic changes in the AT spectra, including a reduction or elimination of the AT splitting, an increase in the critical ${\ensuremath{\Omega}}_{c}$ above which AT splitting occurs, and an increase in the width of the AT spectral lines. Rydberg-atom interactions are controlled by varying the principal quantum number $n$ of the probe Rydberg level; larger values of $n$ correspond to higher dephasing rates ${\ensuremath{\gamma}}_{3}$. Results of numerical calculations are in good agreement with the experiments.