Enhancing the sensitivity of atomic magnetometer with a multi-passed probe light

Atomic magnetometry has spectacular magnetic field sensitivity at room temperature. Here, we theoretically and experimentally investigate the benefits of a multi-pass cell in magnetometers using nonlinear magneto-optical rotation interrogation. Our theoretical analysis shows that there is an improvement in the signal-to-noise ratio (SNR) and consequently on the magnetic field sensitivity by carefully choosing the number of passes through the medium. In our specific case, we experimentally demonstrate a 160% enhancement in the magnetometer sensitivity by using a triple-pass cell, and it is consistent with our analysis on the SNR. This work provides a pathway to evaluate the benefits of multi-pass cells in high-performance atomic magnetometers.