Characterization of ⁸⁷Rb MEMS vapor cells for miniature atomic magnetometers

Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the ⁸⁷Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the ⁸⁷Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the ⁸⁷Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments.