Rydberg electromagnetically-induced transparency in a rubidium vapor cell with buffer gas

Electric field from plasma is notoriously difficult to probe due to its complex and dynamic nature, back-action of Langmuir probes, and limits in spatial resolution. In order to probe the electric field without interfering with the field, we investigate all-optical electric field sensing in the presence of a background gas in the range of several Torr. In this work, we demonstrate Rydberg electromagnetically-induced transparency (EIT) in a vapor cell containing a mixture of rubidium and an inert buffer gas in order to approach conditions that may be found in a background plasma (less the plasma electric fields). We measure frequency shift and spectral broadening of the EIT signals for a range of Rydberg levels, and compare the data to standard EIT reference signals from a buffer-gas-free cell. The results of this study provide important insights into using Rydberg-EIT to measure macroscopic and random electric fields in plasmas.