Low Frequency Rydberg Electrometry in Potassium

Rydberg receivers have promise as an alternative to the electrically small antennas used at low frequencies. However, the realization of a low frequency Rydberg receiver has been hampered by the strong screening effects of the vapor cells at low frequencies. We investigate low frequency Rydberg electrometry using potassium as the active medium. By comparing Stark shifts and sensitivity in rubidium at the few MHz level, we find a notable improvement in the low frequency transmission of potassium vapor cells. We report potassium sensitivity values for frequencies from 500 Hz to 10 MHz in an all-dielectric system. These developments were motivated by a desire to understand and optimize the chemistry at play between the alkali metals and the vapor cell. While the exact mechanism behind the improved low frequency transmission will require additional studies, we hypothesize that the difference arises from a reduced charge donation to the lattice when defect sites react with the alkali. These results highlight the importance of understanding the fundamental chemistry at play in quantum sensors.