Research on the influence of alkali polarization on an all-optical atomic spin magnetometer based on hybrid pumping potassium and rubidium

An all-optical atomic spin magnetometer using a hybrid cell of K and Rb atoms is demonstrated in this paper. Via deriving and solving the Bloch equations, we established the models for the polarization rate of Rb and the magnetometer’s output signal, respectively. In order to achieve the maximum sensitivity, we carried out research on the influence of the pump power on the polarization rate and magnetometer’s output signal. The magnetometer’s sensitivity was found to be proportional to the polarization rate of Rb, which was confined by the pump power. In a certain context, theoretical predictions indicated that the larger the pump power was, the higher magnetometer’s sensitivity that could be realized. However, the theoretical estimate deviated from the experimental results. An analysis of the errors between the actual value and the theoretical value showed that the different molar ratio between the two species of alkali-metal atoms was the primary reason causing the deviation. By comparing the experimental measurement result with simulation result, we found the difference in the molar ratio to be approximate 4 times. After various parameters had been optimized, a sensitivity of 18 fT/Hz^1/2 was achieved by analyzing the signal-to-noise ratio.