We experimentally investigate the nonlinear transmission spectrum of coherent light fields propagating through a Rydberg EIT medium with strong atomic interactions. In contrast to previous investigations, which have largely focused on resonant control fields, we explore here the full two-dimensional spectral response of the Rydberg gas. Our measurements confirm previously observed spectral features for a vanishing control-field detuning, but also reveal significant differences on two-photon resonance. In particular, we find qualitative deficiencies of mean-field models and rate-equation simulations as well as a third-order nonlinear susceptibility that accounts for pairwise interaction effects at low probe-field intensities in describing the nonlinear probe-field response under EIT conditions. Our results suggest that a more complete understanding of Rydberg EIT and emerging photon interactions requires to go beyond existing simplified models as well as few-photon theories.

A. Tebben, C. Hainaut, A. Salzinger, S. Geier, T. Franz, T. Pohl, M. Gärttner, G. Zürn, M. Weidemüller, “Nonlinear absorption in interacting Rydberg electromagnetically-inducedtransparency spectra on two-photon resonance”, Phys. Rev. A 103, 063710 (2021).


Related to Project A05