Characterization of ⁸⁷Rb MEMS vapor cells for miniature atomic magnetometers.

This article focuses on a fast and efficient method to characterize the relaxation properties of micro-electro-mechanical systems (MEMS) atomic vapor cells containing isotopically enriched rubidium-87 (^87Rb), which are critical components in miniaturized atomic magnetometers. Using a single-beam interrogation technique based on the zero-field level crossing resonance effect, the study experimentally determines the transverse relaxation rate and extracts a depolarization coefficient of 0.097 for atom-wall collisions, indicating that polarized ^87Rb atoms can undergo approximately ten collisions with the cell wall before depolarizing. The results show that as the vapor cell radius decreases, alkali-wall collision relaxation increasingly dominates the depolarization process due to the higher surface-to-volume ratio. This characterization approach provides a quantitative means to evaluate anti-relaxation coatings and informs the design of MEMS vapor cells, supporting the advancement of sensitive, miniaturized atomic magnetometers for applications such as biomagnetic field detection in ambient environments.