The spin-exchange-relaxation-free(SERF)atomic magnetometer with ultrahigh sensitive becomes the most effective measurement to analyze the component of the planet in space exploration.In order to improve the sensitivity of the SERF atomic magnetometer,we must avoid the influence on the SERF regime disturbed by environment magnetic field.In this paper we design an active compensation system based on in-situ magnetic measurement to compensate the magnetic disturbance.Firstly,we get the three-axis magnetic field information according to the measurement of pop-laser,then control the current of coil to generate a magnetic field which is opposite and equal to the disturbance,to keep the SERF regime.Finally,we validat the method with the atomic magnetometer experimental setup.The result shows that compared with the manual compensation method,the system can track the magnetic compensation point in real time,reduce the signal noise and compensate the magnetic disturbance successfully,validating the efficiency of the active compensation system and establishing the technique foundation of the production.
The spin-exchange-relaxation-free(SERF)atomic magnetometer with ultrahigh sensitive becomes the most effective measurement to analyze the component of the planet in space exploration.In order to improve the sensitivity of the SERF atomic magnetometer,we must avoid the influence on the SERF regime disturbed by environment magnetic field.In this paper we design an active compensation system based on in-situ magnetic measurement to compensate the magnetic disturbance.Firstly,we get the three-axis magnetic field information according to the measurement of pop-laser,then control the current of coil to generate a magnetic field which is opposite and equal to the disturbance,to keep the SERF regime.Finally,we validat the method with the atomic magnetometer experimental setup.The result shows that compared with the manual compensation method,the system can track the magnetic compensation point in real time,reduce the signal noise and compensate the magnetic disturbance successfully,validating the efficiency of the active compensation system and establishing the technique foundation of the production.
The spin-exchange-relaxation-free (SERF) atomic magnetometer is an ultra-high sensitivity magnetometer, but it must be operated in a magnetic field with strength less than about 10 nT. Magnetic field compensation is an effective way to shield the magnetic field, and this paper demonstrates an in situ triaxial magnetic field compensation system for operating the SERF atomic magnetometer. The proposed hardware is based on optical pumping, which uses some part of the SERF atomic magnetometer itself, and the compensation method is implemented by analyzing the dynamics of the atomic spin. The experimental setup for this compensation system is described, and with this configuration, a residual magnetic field of strength less than 2 nT (±0.38 nT in the x axis, ±0.43 nT in the y axis, and ±1.62 nT in the z axis) has been achieved after compensation. The SERF atomic magnetometer was then used to verify that the residual triaxial magnetic fields were coincident with what were achieved by the compensation system.
The most efficient way to improve the sensitivity of an optically pumped magnetometer (OPM) is to maximize the spin-polarization lifetime of the atoms. The spin exchange relaxation-free (SERF) OPM that operates in zero field environment is one of the most sensitive magnetic sensors. This paper proposes a new three-axis magnetic field compensation method for the single-beam OPM, which zeroes the magnetic field around the sensor to make it work in SERF regime. The method simultaneously employs two modulation magnetic fields and two low-frequency sweeping magnetic fields along two directions perpendicular to the laser beam during the compensation process. The output signal of the photodiode is demodulated at different frequencies, resulting in two outputs that reflect the three components of the magnetic field. This method does not require iterate to tune the three-axis field, which increases the speed of the compensation process significantly. The magnetic field resolutions of the method for the x-axis, y-axis and z-axis are 0.6 pT, 0.6 pT and 5 pt, respectively. A compact OPM with noise density about 20 fT / Hz1/2@10 Hz is developed and tested, demonstrating the feasibility of the method.
Quantum manipulation technology and photoelectric detection technology have jointly facilitated the rapid development of ultra-sensitive atomic spin magnetometers. To improve the output signal and sensitivity of the spin-exchange-relaxation-free (SERF) atomic spin magnetometer, the noises influencing on the output signal and the sensitivity were analyzed, and the corresponding noise suppression methods were presented. The magnetic field noises, including the residual magnetic field noise and the light shift noise, were reduced to approximately zero by employing the magnetic field compensation method and by adjusting the frequency of the pump beam, respectively. With respect to the operation temperature, the simulation results showed that the temperature of the potassium atomic spin magnetometer realizing the spin-exchange relaxation-free regime was 180 °C. Moreover, the fluctuation noises of the frequency and the power were suppressed by using the frequency and the power stable systems. The experimental power stability results showed that the light intensity stability was enhanced 10%. Contrast experiments on the sensitivity were carried out to demonstrate the validity of the suppression methods. Finally, a sensitivity of 13 fT/Hz(1/2) was successfully achieved by suppressing noises and optimizing parameters.
In this study, we demonstrate a non-modulated triaxial magnetic field compensation method for spin-exchange relaxation-free (SERF) atomic magnetometers. We realize simultaneous compensation of the magnetic field along the pump and probe directions by maximizing the first order differential value of the zero-field resonance signal. The magnetic field perpendicular to the pump-probe plane is compensated by zeroing the DC response of the magnetometer. The zero-field resonance is obtained by applying a linearly changed magnetic field along the direction perpendicular to that of the pump-probe plane. The first order differential of the zero-field resonance is acquired using the second order central difference method in real time. Compared with the conventional compensation methods, this method does not involve modulation and demodulation. Therefore, it requires no lock-in amplifier, thus making it more applicable in miniature atomic devices. Moreover, this method compensates the magnetic field along the pump and probe directions using only one criterion. It avoids the cross-talk effect between the pump and probe directions in the presence of non-orthogonal coils. The experiment results show that the compensation resolution is 9 pT, 7 pT and 0.05 pT for the probe, pump, and direction perpendicular to the pump-probe plane, respectively.
The spin-exchange relaxation-free (SERF) atomic magnetometer has high sensitivity for magnetic field measurement, and is of great significance in frontier physics research, biomagnetic detection and other fields. In recent years, as one of the important development directions, its high spatial resolution and multi-channel magnetic field detection capabilities have been further extended. In this paper, based on the three-axis in-situ magnetic field zeroing method (MFZM), the accurate measurement of three-axis static magnetic field is realized, and the using of the digital micro-mirror device (DMD) further supports the measurement of two-dimensional three-axis magnetic field distribution in a specific area. Then, the experimental system was set up and realized the three-axis magnetic field measurement of 25 points within the 4 mm × 4 mm two-dimensional measurement range, and the resolution of each point is a square area with a side length of 0.8 mm. The proposed method based on the SERF atomic magnetometer can measure the triaxial magnetic field in the internal micro-regions in the magnetic field coil, magnetic shield, etc., helping the analysis and evaluation of the high-resolution magnetic field distribution.
We propose a novel method, which leverages the atomic signal itself, to achieve rapid in situ magnetic field compensation in an unknown geomagnetic environment for an unshielded spin-exchange relaxation-free atomic magnetometer. This method employs a strong bias magnetic field aligned with the pump beam direction to maximize the strength of the magnetic field resonance signal. The compensation process is divided into three sequential stages, each focusing on one of the x, y, and z axes by adjusting the magnitude of the bias magnetic field. As a result, the zero magnetic field is identified within 11 seconds, with compensation resolution smaller than 3.0 nT, primarily constrained by the laser power stability. This approach not only enhances the applicability of atomic magnetometers in unshielded environment but also proves effective for in situ magnetic field compensation in shielded environment, such as those used in magnetoencephalography, magnetocardiography, and space science.