Suppression of laser power error in a miniaturized atomic co-magnetometer based on split ratio optimization

A miniaturized atomic spin-exchange relaxation-free (SERF) co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power. A laser power closed-loop control system is usually used to suppress the fluctuation of the laser power. Although this method can greatly eliminate the fluctuation of the in-loop laser power (the feedback laser), it cannot fully eliminate the fluctuation of the out-of-loop laser power (the signal measurement laser). This leads to SERF gyroscope laser power error, which reduces the inertial measurement accuracy. In this paper, the influence mechanism of the split ratio (the ratio of the in-loop laser power to the out-of-loop laser power) on the out-of-loop laser power control accuracy is analyzed by establishing a laser power transmission model inside and outside the loop. Moreover, a method is developed to improve the out-of-loop laser power stability by optimizing the split ratio. Comparative experiments showed that the relative Allan standard deviation of the out-of-loop laser power decreased from 5.48 × 10 −6 to 2.62 × 10 −6 at 100 s, and decreased by an order of magnitude from 1.76 × 10 −5 to 3.30 × 10 −6 at 1000 s. Correspondingly, the rate ramp coefficient in the Allan standard deviation curve of the SERF gyroscope test data decreased from 1.312 (°/h)/h to 0.246 (°/h)/h. And the bias stability increased from 0.032 °/h to 0.019 °/h. Therefore, the proposed method can improve the long-term stability of the probe laser power and effectively suppress the laser power error of the SERF gyroscope.