Rydberg Atom-Based Radio Frequency Electrometry: Hyperfine effects

Hyperfine effects in Rydberg atom-based sensing have been observed for sensing polarization. However, in most work to date, the hyperfine structure involved in the radio frequency transition has been ignored because the residual Doppler widths realized in experiments are larger than the hyperfine energy splittings of the Rydberg states. Recently, we have proposed and demonstrated a collinear three photon scheme for Rydberg atom-based electrometry that has a greatly reduced residual Doppler width, < 500 kHz. In these experiments, we observe the effect of optical pumping and the hyperfine structure of the Rydberg states. We compare the 42P(3/2) -> 41D(5/2) and 42P(3/2) -> 41D(3/2) sensing transitions to show that Rydberg atom hyperfine structure effects can be observed at our spectral resolution. Hyperfine structure and optical pumping can alter the effective transition dipole moments on the sensing transition and can be used to detect polarization of the radio frequency field so our work is important for practical Rydberg atom electric field sensing.