The Optimization and Stabilization of Pump Light Frequency in the Minimized Atomic Magnetometer

In this article, we found an appropriate operating frequency of pump light for stabilizing the light frequency based on the atomic absorption of the vapor cell in the minimized atomic magnetometer. The traditional way to apply this stabilizing method is to stabilize the laser frequency at the absorption peak because its derivative is always zero and not affected by the cell temperature if the pressure shift is suppressed. However, it is observed experimentally that the response amplitude has a drop of up to 40% from the maximum at the absorption peak. It is due to the hyperfine optical pumping, and we explored the applicable condition to obtain the maximum response amplitude by solving the Liouville equation and proved it experimentally as well. Furthermore, we found that under the appropriate pressure, the frequency to obtain maximum response is close to the zero points of the second-order derivative which are not affected by cell temperature as well. Therefore, it is purposed to stabilize the pump laser frequency at these points. It is demonstrated experimentally that the frequency stabilization is the same, while the response amplitude is increased by more than 40% compared to stabilizing at the absorption peak. These results are instructive in improving the performance of minimized atomic magnetometers.