Atom-Based Radio-Frequency Field Calibration and Polarization Measurement Using Cesium nDJ Floquet States

We investigate atom-based electric-field calibration and polarization measurement of a 100-MHz linearly polarized radio-frequency (rf) field using cesium Rydberg-atom electromagnetically induced transparency in a room-temperature vapor cell. The calibration method is based on matching experimental data with the results of a theoretical Floquet model. The utilized 60DJ fine-structure Floquet levels exhibit J-and m(j)-dependent ac Stark shifts and splittings, and they develop even-order rf-modulation sidebands. The Floquet map of cesium 60DJ fine-structure states exhibits a series of exact crossings between states of different mj's which are not rf coupled. These exact level crossings are employed to perform a rapid and precise (+/- 0.5%) calibration of the rf electric field. We also map out three series of narrow avoided crossings between fine-structure Floquet levels of equal mj's and different J's, which are weakly coupled by the rf field via a Raman process. The coupling leads to narrow avoided crossings that can also be applied as spectroscopic markers for rf-field calibration. We further find that the line-strength ratio of intersecting Floquet levels with different mj's provides a fast and robust measurement of the rf field's polarization.