The cell temperature working point optimization of the spin-exchange relaxation-free (SERF) co-magnetometer is studied theoretically and experimentally in this article. Based on the steady-state solution of the Bloch equations, the steady-state response model of the K-Rb- 21 Ne SERF co-magnetometer output signal with cell temperature is established in this paper. And combined with the model, a method to find the optimal working point of the cell temperature that incorporates the pump laser intensity is proposed. The scale factor of the co-magnetometer under different pump laser intensities and cell temperatures is obtained experimentally, and the long-term stability of the co-magnetometer at the different cell temperatures with corresponding pump laser intensities is measured. The results show that the bias instability of the co-magnetometer is reduced from 0.0311 deg/h to 0.0169 deg/h by obtaining the optimal working point of the cell temperature, which verifies the validity and accuracy of the theoretical derivation and the proposed method.
The cell temperature working point optimization of the spin-exchange relaxation-free (SERF) co-magnetometer is studied theoretically and experimentally in this article. Based on the steady-state solution of the Bloch equations, the steady-state response model of the K-Rb- 21 Ne SERF co-magnetometer output signal with cell temperature is established in this paper. And combined with the model, a method to find the optimal working point of the cell temperature that incorporates the pump laser intensity is proposed. The scale factor of the co-magnetometer under different pump laser intensities and cell temperatures is obtained experimentally, and the long-term stability of the co-magnetometer at the different cell temperatures with corresponding pump laser intensities is measured. The results show that the bias instability of the co-magnetometer is reduced from 0.0311 deg/h to 0.0169 deg/h by obtaining the optimal working point of the cell temperature, which verifies the validity and accuracy of the theoretical derivation and the proposed method.
Abstract The fluctuation of the vapor cell temperature leads to the variations of the density of the alkali metal atoms, which seriously damages the long-term stability of the spin-exchange relaxation-free (SERF) comagnetometer. To address this problem, we propose a novel method for suppressing the cell temperature error by manipulating the probe laser frequency. A temperature coefficient model of the SERF comagnetometer is established based on the steady-state response, which indicates that the comagnetometer can be tuned to a working point where the output signal is insensitive to the cell temperature fluctuation, and the working point is determined by the relaxation rate of the alkali metal atoms. The method is verified in a K−Rb− 21Ne comagnetometer, and the experimental results are consistent with the theory. The theory and method presented here lay a foundation for the practical applications of the SERF comagnetometer.
Bias stability is one of the most important characteristics of a spin-exchange relaxation-free gyroscope (SERFG). The previous research on the SERFG has demonstrated that atomic density fluctuation induced by the vapor cell temperature fluctuations in a SERFG limits its bias stability. In this paper, a steady-state response model of a SERFG dependent on the vapor cell temperature is established, and a method to reduce the vapor cell temperature error of the SERFG is developed. By adjusting the vapor cell temperature, the SERFG can be tuned to a working point where the output signal is insensitive to the cell temperature fluctuation, i.e., the insensitive point, so that the bias error induced by cell temperature fluctuations can be effectively suppressed. The proposed method is verified by experiments, and experimental results are in good agreement with the model. By using the proposed method, SERFG drift was reduced from 0.051 deg/h to 0.028 deg/h without adjusting the wavelength of the probe laser. This study presents a way to improve the SERFG performance, which is of reference value for quantitative error analysis and miniaturization in atomic gyroscopes.
Abstract Spin-exchange relaxation-free (SERF) co-magnetometers have promising applications in both inertial navigation and fundamental physics experiments. However, the fluctuation in the spin polarization caused by the probe beam has a non-negligible influence on the co-magnetometer signal. In this paper, a theoretical model containing three parameters of the probe beam is established by extending the coupled Bloch equation. Based on this model, the influence of probe power density on the transient and steady-state response of the SERF co-magnetometer is analyzed. According to the transient response model, a new measurement method for transverse optical pumping of the probe beam is proposed. Then, for the steady-state response model, a steady-state error suppression method is suggested by adjusting the degree of circular polarization of the probe beam. Eventually, the suppression method is used to refine the SERF co-magnetometer, achieving a suppression rate of 70.31% in transverse electron spin polarization fluctuations, thus improving the co-magnetometer to a stability of 0.0079∘ h−1. To our knowledge, this is better than what has been reported so far.
This paper presents a method to reduce the vapor cell temperature error of the spin-exchange-relaxation-free (SERF) magnetometer. The fluctuation of cell temperature can induce variations of the optical rotation angle, resulting in a scale factor error of the SERF magnetometer. In order to suppress this error, we employ the variation of the probe beam absorption to offset the variation of the optical rotation angle. The theoretical discussion of our method indicates that the scale factor error introduced by the fluctuation of the cell temperature could be suppressed by setting the optical depth close to one. In our experiment, we adjust the probe frequency to obtain various optical depths and then measure the variation of scale factor with respect to the corresponding cell temperature changes. Our experimental results show a good agreement with our theoretical analysis. Under our experimental condition, the error has been reduced significantly compared with those when the probe wavelength is adjusted to maximize the probe signal. The cost of this method is the reduction of the scale factor of the magnetometer. However, according to our analysis, it only has minor effect on the sensitivity under proper operating parameters.
Heating the alkali metal vapor cell to obtain high atomic density is a prerequisite for realizing the high-precision measurement for spin-exchange relaxation-free (SERF) co-magnetometer. However, the thermo-magnetic and thermo-optical coupling noise caused by the temperature diffusion from the alkali vapor cell is one of the main factors restricting the co-magnetometer performance at present. Here the influence of heating on the SERF co-magnetometer was comprehensively studied, and the thermal error model of the system was established. A novel heat insulation structure for the co-magnetometer was designed, and the effectiveness was verified through monitoring of characteristic temperature points. Compared to the conventional oven support, the average maximum temperature difference within 12 h of the optical path and magnetic shielding systems (OPMSS) decreased by 52%, the bias instability of the co-magnetometer decreased by 24%, and the noise of the co-magnetometer at 1 Hz decreased by 33%. The experimental results demonstrate that this method reduces the temperature fluctuation of the OPMSS, effectively suppresses the thermal coupling noise, and thus improves the performance of the SERF co-magnetometer. Moreover, this method is also applicable to other quantum sensors based on alkali metal vapor cell.
As a novel quantum sensor utilizing atomic spin coupling mechanisms, spin-exchange relaxation-free (SERF) comagnetometers demonstrate promising applications in precision metrology such as magnetic field and rotation sensing. However, the ultra-high precision measurement capability exhibits vulnerability to multiple disturbance factors, with pump light intensity fluctuations emerging as a critical instability source that compromises operational reliability during prolonged measurements. In this paper, a model-driven paradigm for pump light intensity error suppression in SERF comagnetometers is proposed. The nonlinear dynamics are rigorously linearized via Taylor expansion within their valid range to construct a state-space model, ultimately deriving the pump light intensity frequency response model. The proposed methodology undergoes experimental validation on a K-Rb-21Ne comagnetometry platform, confirming the predictive capability for stability degradation mechanisms. Through theoretical analysis and experimental verification, this study reveals that magneto-optical non-orthogonality, which introduces a differential component in the light intensity transfer function, creates an approximate proportional relationship between the output signal and pump light intensity within the operating bandwidth. Light intensity noise is decomposed, and light intensity errors are quantitatively evaluated via the frequency response model. To address this critical issue affecting inertial measurement accuracy, a closed-loop control-based suppression method with optimized feedback gain is proposed. By dynamically adjusting the closed-loop feedback gain through real-time intensity monitoring, the intensity instability associated with optical pumping is suppressed from 0.56% to 0.14%, concomitant with a 2.8-fold improvement in the long-term stability of the SERF comagnetometer.