We investigate two-photon Autler-Townes splitting and strong-field effects of ${}^{85}\mathrm{Rb}$ Rydberg atoms in a room-temperature vapor cell. To observe the level structure we employ electromagnetically induced transparency. We first study the two-photon $62S_{1/2}\text{−}63S_{1/2}$ microwave transition using an electric-field reference measurement obtained with the one-photon $62S_{1/2}\text{−}62P_{3/2}$ transition. We then study the $61D_{5/2}\text{−}62D_{5/2}$ transition where the microwave electric-field range is extended up to $\sim 40\mathrm{V}/\mathrm{m}$. A Floquet analysis is used to model field-induced level shifts and state-mixing effects present in the strongly driven quantum systems under consideration. Calculations are found to be in good agreement with experimental observations.

• Received 10 August 2014

DOI:https://doi.org/10.1103/PhysRevA.90.043419