Observation of effects of inter-atomic interaction on Autler-Townes splitting in coldRydberg atoms

We demonstrate the effect of inter-atomic interaction in highly excited Rydberg atoms via Autler- Townes splitting in cold atoms. We measure the Autler-Townes (AT) splitting of the 5S 1/2 , F = 2 → 5P 3/2 , F ′ = 3 transition of 87Rb atoms arising due to the strong coupling of the transition via the cooling beams used for the magneto-optical trap (MOT). The AT splitting is probed using a weakly coupled transition from 5P 3/2 , F ′ = 3 state to highly excited Rydberg states for a wide range of principal quantum numbers (n = 35−117). We observe the AT splitting via trap-loss spectroscopy in the MOT by scanning the probe frequency. We observe a drastic increase in the broadening of the AT splitting signal as a result of interaction-induced dephasing effect in cold Rydberg atoms for highly excited Rydberg states with principal quantum number n > 100. We explain our observations using theoretical modelling and numerical simulations based on the Lindblad Master equation. We find a good agreement of the results of the numerical simulation with the experimental measurements.