Low frequency electric field sensing with a Rydberg beam

Abstract

We present a method for performing low frequency electric field sensing via ionization detection of Rydberg atoms in a collimated atomic beam. A collimated beam avoids much of the electric field screening effects that are common in warm vapor cells due to the accumulation of alkali-metal atoms on glass surfaces. Further, a beam facilitates a spatially separated region for high signal-to-noise readout via ionization detection. Using this approach, we measure DC Stark shifts from external fields with frequencies as low as 1 Hz. The sensor demonstrates a sensitivity of better than 1 mV/m$\sqrt{\rm {Hz}}$ for frequencies above 20 Hz and $0.14(4)$ mV/m$\sqrt{\rm {Hz}}$ above 500 Hz with a linear dynamic range of over 50 dB.

Figures (10)

• Figure 1: Overview of the experimental apparatus; (a) and (b) not drawn to scale. (a) A collimated $^{85}$Rb beam passes through lasers exciting a portion of the atoms to a Rydberg state. These atoms pass through a set of mesh plates that ionize the Rydberg atoms and deflect the ions towards a CEM detector. (b) Two plates external to the vacuum system produce a low frequency electric field at the excitation region in the chamber. A blue LED is used to reduce time varying perturbations on the ion signal. (c) CAD model of the vacuum system and atomic beam source. Some components have been made transparent to aid in visual clarity.
• Figure 2: Spatial characteristics of the atomic beam at the location of the laser excitation region parallel (a) and perpendicular (b) to the laser propagation directions. Red curves are simulated spatial profiles while black markers are experimental values. (c) Image of the collimating nozzle and surrounding cold pump.
• Figure 3: Energy level and laser scheme for excitation to the Rydberg state. (a) Example ion spectra for 60P$_{3/2}$. (b) Observed oscillation of the ion signal when a 1 Hz signal is applied externally to the system while the Rydberg laser is locked to the side of the ion spectra.
• Figure 4: Theoretical Stark map of $\left|101P_{3/2},m_{\rm J}=1/2\right>$ and $\left|101P_{3/2},m_{\rm J}=3/2\right>$ showing energy shifts and state mixing as a function of electric field amplitude. The colorbar indicates the fraction of the initial state in each atom eigenstate $\left|\mu\right>$.
• Figure 5: (a) Example DC Stark shifts and splitting of the $m_{\rm{J}}$ states for various voltages applied to the external field plates. Measured 2D Stark maps with theoretical fits (red curves) for 55P$_{3/2}$ (b) and 60P$_{3/2}$ (c). The theoretical fits are used to determine the conversion factor between the voltage applied to the external plates and electric field magnitude at the laser excitation region in the system.