Longitudinal spin-relaxation optimization for miniaturized optically pumped magnetometers

TL;DR

This paper demonstrates a method to optimize nitrogen buffer gas pressure in microfabricated cesium vapor cells for optically pumped magnetometers, enhancing their coherence time and sensitivity through post-fabrication tuning.

Contribution

It introduces a post-bond nitrogen buffer gas pressure tuning technique via localized heating, enabling tailored optimization of magnetometer performance after fabrication.

Findings

Minimum longitudinal relaxation rate of 140 Hz at 115 Torr nitrogen pressure

Achieved magnetic sensitivity as low as 130 fT/√Hz

Optimal nitrogen pressure can be set post-fabrication for various applications

Abstract

The microfabrication of cesium vapor cells for optically pumped magnetometry relies on optimization of buffer gas pressure in order to maximize atomic coherence time and sensitivity to external magnetic signals. We demonstrate post-bond nitrogen buffer gas pressure tuning through localized heating of an integrated micro-pill dispenser. We characterize the variation in the intrinsic longitudinal relaxation rate, $\gamma_{10}$, and magnetic sensitivity, as a function of the resulting nitrogen buffer gas pressure. Measurements are conducted through employing an optically pumped magnetometer operating in a free-induction-decay configuration. $\gamma_{10}$ is extracted across a range of nitrogen pressures between $\sim$~60~-~700~Torr, measuring a minimum of 140~Hz at 115~Torr. Additionally, we achieve sensitivities as low as 130 ~fT/$\sqrt{\text{Hz}}$ at a bias field amplitude of $\sim 50~\mu$T. With the optimal nitrogen buffer gas pressure now quantified and achievable post-fabrication, these mass-producible cells can be tailored to suit a variety of sensing applications, ensuring peak magnetometer performance.