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Advanced Quantum Technologies

Reflection‐Compensated Orthogonal Non‐Overlapping Uniform Pumping Scheme For Triaxial Serf Atomic Magnetometers

Ying Liu, M.K. Song, Binyue Huang, Yuxuan An, Tong Jin, Zhanchao Liu, Yueyang Zhai

Published Jul 1, 2026• 0 citations
Publisher

Abstract

ABSTRACT Triaxial spin‐exchange relaxation‐free (SERF) atomic magnetometer has attracted widespread attention for its capability of measuring the total magnetic field vector information. In this paper, we propose a triaxial SERF atomic magnetometer through orthogonal non‐overlapping pumping beam with improved atom spin polarization spatial uniformity by using a uniformized pump beam and reflection compensation . The homogenized beams are adopted to achieve uniform transverse polarization, while double‐pass reflection compensation is integrated to realize uniform longitudinal polarization. The polarizability distribution based on an effective optical path‐length formalism was obtained via theoretical simulation. The bandwidth, dispersion curves, stability, and sensitivity were experimentally analyzed under three configurations: uniformized pump beam , gaussian pump beam‐reflection compensation , and uniformized pump beam‐reflection compensation . Results of experiments reveal that the proposed configuration enhances three‐axis bandwidth by roughly 10 and improves X, Y, and Z sensitivities by approximately 35, 60, and 30, respectively, achieving sensitivities of 20.56 fT/(X), 30.75 fT/(Y) and 20.54 fT/(Z) at 140 and 2 mW. These results demonstrate a structurally simple yet highly effective approach for achieving high uniformity and stability in three‐axis vector magnetic sensing, with strong potential for applications such as spatial magnetic‐field mapping and bio‐magnetic measurement research.

DOI
10.1002/qute.70380

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IEEE Transactions on Instrumentation and Measurement•Jan 1, 2025•7 citations
ABSTRACT Triaxial spin‐exchange relaxation‐free (SERF) atomic magnetometer has attracted widespread attention for its capability of measuring the total magnetic field vector information. In this paper, we propose a triaxial SERF atomic magnetometer through orthogonal non‐overlapping pumping beam with improved atom spin polarization spatial uniformity by using a uniformized pump beam and reflection compensation . The homogenized beams are adopted to achieve uniform transverse polarization, while double‐pass reflection compensation is integrated to realize uniform longitudinal polarization. The polarizability distribution based on an effective optical path‐length formalism was obtained via theoretical simulation. The bandwidth, dispersion curves, stability, and sensitivity were experimentally analyzed under three configurations: uniformized pump beam , gaussian pump beam‐reflection compensation , and uniformized pump beam‐reflection compensation . Results of experiments reveal that the proposed configuration enhances three‐axis bandwidth by roughly 10 and improves X, Y, and Z sensitivities by approximately 35, 60, and 30, respectively, achieving sensitivities of 20.56 fT/(X), 30.75 fT/(Y) and 20.54 fT/(Z) at 140 and 2 mW. These results demonstrate a structurally simple yet highly effective approach for achieving high uniformity and stability in three‐axis vector magnetic sensing, with strong potential for applications such as spatial magnetic‐field mapping and bio‐magnetic measurement research.
Abstract We display a single-beam triaxial spin-exchange relaxation-free (SERF) atomic magnetometer by utilizing two orthogonal transverse modulation fields perpendicular to the light. The magnetic field’s three-axis vector components can be extracted simultaneously and independently from the transmitted light by lock-in amplifiers with reference to the different demodulated frequencies. We find that the residual magnetic field is a significant factor that could affect triaxial coupling, and specially the influence of the z -axis remanence on xy -axis coupling is studied in detail. Under the optimal parameters, the three-axis sensitivities are 20 fT Hz − 1 / 2 in the x - and y - axis, and 230 fT Hz − 1 / 2 in the z -axis. Meanwhile, the three-axis bandwidths are 110 Hz, 138 Hz and 211 Hz in the x -, y - and z -axis, respectively. The proposed single-beam triaxial SERF atomic magnetometer could be used to construct a compact and low-cost atomic sensor that is particularly suitable for the vector measurement of the biomagnetic such as magnetoencephalography and magnetocardiography.
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.
Abstract High-sensitivity triaxial magnetic field measurements are crucial in various scientific and industrial applications, with spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) standing out for their exceptional sensitivity. However, conventional methods for achieving triaxial measurements in SERF magnetometers typically involve multiple modulated magnetic fields, which introduce crosstalk challenges in array-based configurations. We propose a static bias magnetic field assisted optical modulation triaxial AM to address this limitation. In this configuration, the detuned circularly polarized light is utilized to achieve synchronous modulation of the fictitious magnetic field and pumping rate while incorporating a static bias magnetic field to generate a transverse projection component. We develop a comprehensive triaxial response model that fully considers the effects of the longitudinal spin polarization deflection. Building upon this model, we derive the relationship between the transverse spin component and the triaxial magnetic field and introduce parameter optimization methods to obtain optimal parameters, thus enabling triaxial measurements of 12 fT Hz −1/2 , 10 fT Hz −1/2 , and 15 fT Hz −1/2 along the x-, y -, and z -axes. Our approach offers significant advantages over existing methods, particularly in minimizing crosstalk and mitigating spin-exchange relaxation introduced by multiple modulated magnetic fields. Moreover, the effective detection of simulated magnetocardiography signals highlights the practical applicability and reliability of the proposed method in real-world scenarios.
Abstract Atomic spin comagnetometers based on the spin-exchange relaxation-free (SERF) effect offer significant potential for inertial sensing and support the development of long-endurance, high-precision navigation technologies. However, limited nuclear spin polarization constrains the long-term stability of these systems. Here, a flat-top optical pumping configuration is introduced for SERF comagnetometers, expanding the uniform-intensity region of the beam to approximately 62 % , which enhances atomic polarization by around 19 % and improves magnetic noise suppression by 32 % . Experimental results demonstrate notable improvements in both sensitivity and long-term stability, highlighting the effectiveness of flat-top beams in overcoming atomic polarization uniformity limitations and advancing SERF co-magnetometer performance.
In this paper, we propose a three-axis atomic magnetometer (AM), in which one light beam is divided into two orthogonal spatially separated pump beams by a lateral displacement polarized beam splitter and reflector mirrors; this scheme suppresses the three-axis crosstalk caused by the interaction between the two beams and atoms in the cell. When the AM operates in the direct-current (DC) mode, the three-axis crosstalk is significant. To solve this problem, three modulation fields with the same amplitudes, frequencies, and different phases are applied, which allow the AM operated in modulation mode to perform a highly sensitive synchronous and independent measurement of the three-axis magnetic field with low crosstalk. The experimental results showed that the three-axis crosstalk was less than 2%. In the modulation mode, the sensitivities were 22, 23, and 26 fT/Hz1/2 on the x-, y-, and z-axes, respectively. The 3-dB bandwidths of the three axes were 126, 124, and 112 Hz. In addition, we demonstrated a three-axis in-situ magnetic compensation method with a magnetic compensation accuracy of the pT level in the DC mode. The proposed triaxial AM can be easily miniaturised and used in biomedical applications, such as in magnetocardiography and magnetoencephalography.
This study proposes an in situ method for measuring the equilibrium spin polarization and its longitudinal spatial distribution in a spin-exchange relaxation-free (SERF) atomic magnetometer. The total relaxation rate was determined by analyzing the steady-state response of the magnetometer to the triaxial magnetic field. The transfer coefficient between spin polarization along the probe beam axis and the steady-state response was derived from the optical depth of the probe light and the incident/transmitted power through the vapor cell. By applying a DC magnetic field along the sensitive axis and combining the total relaxation rate with the transfer coefficient, the equilibrium spin polarization value under zero-field conditions was obtained. The equilibrium spin polarization distribution along the pump beam propagation direction was measured, showing consistent trends with simulation results, with a maximum relative error of less than 5%. The expanded uncertainty of the proposed equilibrium spin polarization measurement method ranges from 0.8% to 9.7%. The advantages of this method include no requirement for additional optical field or magnetic field modulation, immunity to temperature and temperature gradients, and the capability to directly determine the equilibrium spin polarization value.