Influence of Buffer-Gas Pressure Inside Micro Alkali Vapor Cells on the Performance of Chip-Scale SERF Magnetometers

Spin-exchange-relaxation-free (SERF) optical atomic magnetometers are facing the challenges of dramatic decrease of sensitivity when the alkali vapor cells become small. This paper focuses on the sensitivity improvement of the chip-scale atomic magnetometer (CSAM) by changing buffer-gas pressures inside the microfabricated vapor cells. The rubidium vapor cells with three different buffer-gas pressures were tested in the SERF magnetometer. The influences of vapor cell temperature and pumping laser power on the device sensitivity are also characterized for further optimization. Results show that the three atomic vapor cells, with N ₂ buffer-gas pressure of 0.20, 0.88, and 2.35 amg, have sensitivities of 900, 500, and 150 fT/Hz ^1/2 , respectively. Results indicated that when the alkali vapor cells continue to be smaller, high buffer-gas pressure would provide an effective way to reduce the wall collision and improve the performance of CSAMs.