Rydberg Atom-based Electrometry Using a Self-heterodyne Frequency Comb Readout and Preparation Scheme

Recently, Rydberg atom spectroscopy in room temperature vapor cells has arisen as a promising method for electromagnetic (EM) field sensing. In contrast to traditional antennas, atomic EM field sensors are all-dielectric, minimizing perturbations of the field of interest, and self-calibrating. These sensors offer extraordinary carrier bandwidth, stability, accuracy and reproducibility. Atomic EM sensors have applications in radar, communications, and test and measurement, but implementation of these sensors is challenging, partly because of the sophisticated laser systems required. Here, we demonstrate the use of optical frequency comb spectroscopy to detect two-photon electromagnetically induced transparency (EIT) and measure EM fields in a massively parallel fashion while reducing the complexity of the optical setup. Using a flat, quasi-continuous optical frequency comb generated through electro-optic modulation, we read-out EIT in a cesium vapor cell using self-heterodyne spectroscopy, resolving linewidths of less than 5 MHz both with and without laser locking, enabling a significant reduction in the sophistication of the required laser systems. We further demonstrate radio frequency EM field sensing through Autler-Townes splitting of the enhanced transmission signal. The frequency comb technique eliminates the need for laser scanning and enables the real-time determination of the full EIT peak line structure, which is beneficial for many applications. We discuss the potential to apply this method to the detection of pulsed EM fields along with avenues to improve the speed and sensitivity in future measurements.