Investigation of Fluorescence vs. Transmission Readout for Three-Photon Rydberg Excitation used in Electrometry

Rydberg electrometry in alkali vapors typically utilizes two-photon electromagnetically induced transparency (EIT) for readout. In this type of readout, the signal from the Rydberg state is typically <5% of the total power of the probe optical field. This facet pushes signal-to-noise (SNR) down and limits sensitivity. We perform EIT and fluorescence measurements on the Rydberg state in a three-photon excitation scheme in Cesium and compare the two methods. We demonstrate the best recorded EIT sensitivity in a three-photon system to date of 30 μVm^-1Hz^-1/2. Furthermore, we show even better electric field sensitivity with the fluorescence measurement, down to 7 μVm^-1Hz^-1/2. Also, we characterize the rise and fall times of the fluorescence signal and characterize the sources of black body radiation-induced state transfer and collision-based state transfer. This measurement can help characterize different Rydberg states in a vapor cell, similar to work done in atomic beams.