Lifetime extension of Rubidium vapor cells by Al₂O₃ coating

Atomic vapor cells, where atoms undergo thermal motion, are actively studied in magnetometers, gyroscopes, quantum light interactions, and time synchronizations due to their simplicity of the system. In particular, in the spin exchange relaxation-free (SERF) regime, a highly sensitive magnetometer, the atomic vapor system is heated to 150 °C to maintain a high number of alkali atoms. However, in general, when an atomic vapor cell made of glass is exposed to high temperatures, alkali atoms permeate and adsorb onto the glass surface, causing a decrease in their number. This loss eventually renders the atomic vapor cell unusable. To address this issue, we demonstrate that coating the inner surface of atomic vapor cells with Al₂O₃, which has high resistance to alkali atoms, reduces rubidium consumption and extends the cell lifetime. In this study, we compared the lifetimes of two atomic vapor cells: a cubic cell with an inner diameter of 5.5 mm fabricated using the tip-off method, and the other cell coated on its inner surface with Al₂O₃ using the electron beam deposition method. The lifetime of the atomic vapor cell is determined by the rubidium density inside the cell, and the amount of rubidium is monitored through absorption spectroscopy measurement of the rubidium D₁ transition.