We present a low-power bidirectional alkali vapor source based on solid-state electrochemistry. The device comprises a solid electrolyte, beta”-alumina, in between two electrodes. One electrode contacts the alkali vapor inside the vapor cell and consists of a uniform 10nm glassy carbon layer covered with widely spaced Pt lines. The other electrode, which serves as a solid-state alkali reservoir, consists of widely space Pt lines and graphite particles.
The thin glassy carbon layer getters rubidium until it becomes saturated. When a positive voltage is applied across the device electrodes, alkali atoms in the glassy carbon layer are oxidized and alkali ions transport into the solid electrolyte. This reduces the rubidium concentration in the glassy carbon and, rubidium vapor gettering resumes, causes rubidium vapor pressure reduction. Alkali ions are reduced at the other electrode and alkali atoms are intercalated in the graphite in the solid state alkali reservoir to maintain ion balance in the solid electrolyte. When a negative voltage is applied the process reverses. Alkali ions are reduced at the glassy carbon electrode, thus quickly saturating the glassy carbon with alkali atoms to stop rubidium gettering and further providing additional rubidium to evaporate and increase the rubidium vapor pressure in the vapor cell. Reversible actuation with this device has been demonstrated with voltages as low as 5 V and peak power as low as 3.4 mW. Furthermore, we will present the use of this device in a feedback loop to control Rb vapor density. The ability to electrically control alkali vapor pressure at low power is an enabling advance for cold atom microsystems.
This material is based upon work supported by the Defense Advanced Research Projects Agency (DARPA) and Space and Naval Warfare Systems Center Pacific (SSC Pacific) under Contract No. N66001-15-C-4027. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DARPA or SSC Pacific.
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