Magnetic resonance linewidths independent with the laser linewidth in coherent population trapping (CPT) magnetometers

Coherent population trapping (CPT) magnetometers are the magnetic measuring instrument that utilize the interference effect between light and atoms. It has a broad range of applications in weak magnetic measurement. However, current CPT magnetometers have low sensitivity, which does not satisfy the ultra-high sensitivity requirements of weak magnetic measurement. This paper is aimed to improve this problem by studying the relationship between the sensitivity of CPT magnetometer and the laser linewidth. It has been concluded that the magnetic resonance linewidth of the CPT system remains independent of the laser linewidth according to the Liouville equation, firstly. Furthermore, the correctness of this theory has been verified through design experiments. Additionally, we have identified certain issues that require attention in the miniaturization and chip-scale CPT magnetometer on vertical cavity surface emitting laser (VCSEL).