Abstract The optically pumped atomic magnetometer (OPAM) has emerged as an advanced instrument for magnetic field detection. However, the performance of conventional OPAMs is constrained by factors such as non‐uniform atomic polarization and insufficient precision in system polarization control. In this study, a bidirectional‐pump OPAM based on spin‐decoupled metasurface is presented and experimentally demonstrated. By designing a metasurface structure with a predefined phase distribution, the system generates two circularly polarized (CP) lights with distinct chirality and one linearly polarized (LP) light. Two beams of the CP light are directed in opposite directions along both sides of the cell, which effectively mitigates the polarization gradient within the cell and enhances the stability of the system. Additionally, the use of zero‐order LP light as the probe light for the system enhances energy utilization efficiency while simplifying the system architecture. The experimental results demonstrate that the OPAM based on metasurface successfully realizes precise control of atomic spin polarization. The proposed OPAM is capable of performing high‐precision magnetic field measurements, and the sensitivity has been improved to 1.85 pT/Hz 1/2 . This research not only advances the application of metasurfaces in quantum precision measurement but also offers a novel approach for enhancing the performance of atomic magnetometers.
Abstract The optically pumped atomic magnetometer (OPAM) has emerged as an advanced instrument for magnetic field detection. However, the performance of conventional OPAMs is constrained by factors such as non‐uniform atomic polarization and insufficient precision in system polarization control. In this study, a bidirectional‐pump OPAM based on spin‐decoupled metasurface is presented and experimentally demonstrated. By designing a metasurface structure with a predefined phase distribution, the system generates two circularly polarized (CP) lights with distinct chirality and one linearly polarized (LP) light. Two beams of the CP light are directed in opposite directions along both sides of the cell, which effectively mitigates the polarization gradient within the cell and enhances the stability of the system. Additionally, the use of zero‐order LP light as the probe light for the system enhances energy utilization efficiency while simplifying the system architecture. The experimental results demonstrate that the OPAM based on metasurface successfully realizes precise control of atomic spin polarization. The proposed OPAM is capable of performing high‐precision magnetic field measurements, and the sensitivity has been improved to 1.85 pT/Hz 1/2 . This research not only advances the application of metasurfaces in quantum precision measurement but also offers a novel approach for enhancing the performance of atomic magnetometers.
Abstract The powerful light field manipulation capability of metasurfaces offers a novel development perspective for the quantum precision measurement. By applying the phase-gradient metasurface (PGM) to atomic magnetometers (AMs), we have proposed and experimentally demonstrated a new type of compact single-beam elliptically polarized atomic magnetometers (EPAMs). Employing the fabricated chiral beam splitter PGM with high cross-polarization transmittance, a new atomic spin chirality detection method was devised, enabling the ultra-high sensitivity for extremely weak magnetic field measurement and achieving a high sensitivity of 2.67 pT/Hz1/2 under an external magnetic field of approximately 10,000 nT. The new AMs combine the pumping and probing polarized light, achieving a compact design. The fabricated PGM has a size of only 3 mm × 3 mm × 0.7 mm, which is beneficial for the miniaturization and integration of AMs. This work effectively expands the application of metasurfaces in the field of quantum precision measurement, and also provides a new viewpoint for the design and development of high-sensitivity and miniaturized AMs.
ABSTRACT Single‐beam optically pumped atomic magnetometers (OPAMs) are promising tools for biomagnetic measurements in nonzero‐field environments owing to their high sensitivity and compactness. However, the angle between the external bias magnetic field and the pump light affects the spin polarization of the atomic ensemble, thereby influencing the magnetometer performance and making the optimization of the magneto‐optical angle essential. In this study, a spatially resolved steady‐state spin polarization model incorporating the magneto‐optical angle is established for the first time, and an analytical expression of the spin precession signal under RF magnetic field excitation is derived. It is demonstrated that an optimal angle exists at which the magnetometer exhibits the maximum response and the highest sensitivity, which is experimentally determined to be 26° in our single‐beam OPAM. At this angle, the combined influence of the steady‐state spin polarization, spin precession projection, transmitted light intensity, and transverse spin relaxation reaches an optimal overall state, leading to a 14% enhancement in sensitivity and a 32% reduction in detection noise compared with the conventional 45° configuration. These findings provide guidance for optimizing the experimental parameters of single‐beam OPAMs for weak magnetic signal detection in nonzero‐field environments.
ABSTRACT The Bell‐Bloom‐type optically‐pumped atomic magnetometers are well‐suited for weak geomagnetic field detection. However, conventional single‐beam pumping introduces an atomic spin polarization gradient, which limits the measurement accuracy and sensitivity. To address this issue, this paper proposes and experimentally demonstrates a Bell‐Bloom‐type rubidium FID magnetometer scheme integrating orthogonally polarized counter‐propagating pumping and multi‐pass probe detection. This design homogenizes the atomic spin polarization distribution and suppresses light shifts and power broadening. This uniform polarization, in turn, allows the five‐pass probe configuration to achieve a significantly larger signal amplitude. Experimental results reveal that, compared with the traditional single‐beam pumping and single‐pass detection scheme, the proposed magnetometer achieves a remarkable improvement in magnetic field measurement accuracy, and the magnetic field sensitivity is improved from 18.9 to 3.1 pT/. Notably, the two techniques work synergistically, yielding a 6.1‐fold sensitivity enhancement that far exceeds their individual gains. This work provides an effective technical approach and reference for optimizing the performance of atomic magnetometers and their applications in precision measurement fields.
Single-beam optically pumped atomic magnetometers (OPAMs) represent promising candidates for applications in geomagnetic field monitoring, biomedicine, and various other precision sensing domains owing to their exceptional sensitivity, high measurement accuracy, and cost-effectiveness. However, in orientation-based OPAMs utilizing circularly polarized light (CPL) pumping, the off-resonant light introduces light shift. The light shift acts as an additional magnetic field, reducing the measurement accuracy of OPAMs. Moreover, the dependence of the light shift on light intensity and frequency facilitates the conversion of light noise into magnetic noise, thereby degrading the sensitivity of OPAMs. In this study, we propose an optical pumping scheme based on space division multiplexing light (SDML) to suppress the light shift in OPAM. The approach employs two orthogonally polarized linearly polarized beams with a controlled phase difference to generate a spatially periodic distribution of left- and right-handed CPL. Optical pumping with the SDML induces oppositely directed light shifts in distinct spatial regions that effectively cancel each other. Finally, it is verified by experiments that the light shift is greatly suppressed based on SDML. Under detuned SDML pumping, both the light shift and light intensity noise are suppressed by over 50%, while maintaining a sensitivity comparable to that achieved with conventional CPL pumping. The proposed method demonstrates significant potential for magnetometers in light-noise-prone environments, and it can be generalized to other orientation-based magnetometers that rely on CPL pumping.
The Bell-Bloom-type optically pumped atomic magnetometers are well suited for weak geomagnetic field detection. However, conventional single-beam pumping introduces an atomic spin polarization gradient, which limits the measurement accuracy and sensitivity. To address this issue, this paper proposes and experimentally demonstrates a Bell-Bloom-type rubidium FID magnetometer scheme integrating orthogonally polarized counter-propagating pumping and multi-pass probe detection. This design homogenizes the atomic spin polarization distribution and suppresses light shifts and power broadening effects induced by the pump beam. Meanwhile, the five-pass probe configuration significantly enhances the signal amplitude. Experimental results reveal that, compared with the traditional single-beam pumping and single-pass detection scheme, the proposed magnetometer achieves a remarkable improvement in magnetic field measurement accuracy, and the magnetic field sensitivity is improved from 18.9 pT/\sqrt{Hz} to 3.1 pT/\sqrt{Hz}. This work provides an effective technical approach and reference for optimizing the performance of atomic magnetometers and extending their applications in integrated arrays.
Abstract Emerging miniaturized atomic sensors such as optically pumped magnetometers (OPMs) have attracted widespread interest due to their application in high‐spatial‐resolution biomagnetism imaging. While optical probing systems in conventional OPMs require bulk optical devices including linear polarizers and lenses for polarization conversion and wavefront shaping, which are challenging for chip‐scale integration. In this study, an integrated optical probing scheme based on localized‐interference metasurface for chip‐scale OPM is developed. Our monolithic metasurface allows tailorable linear polarization conversion and wavefront manipulation. Two silicon‐based metasurfaces namely meta‐polarizer and meta‐polarizer‐lens are fabricated and characterized, with maximum transmission efficiency and extinction ratio (ER) of 86.29 % and 14.2 dB for the meta‐polarizer as well as focusing efficiency and ER of 72.79 % and 6.4 dB for the meta‐polarizer‐lens, respectively. A miniaturized vapor cell with 4 × 4 × 4 mm 3 dimension containing 87 Rb and N 2 is combined with the meta‐polarizer to construct a compact zero‐field resonance OPM for proof of concept. The sensitivity of this sensor reaches approximately 9 fT/Hz 1/2 with a dynamic range near zero magnetic field of about ±2.3 nT. This study provides a promising solution for chip‐scale optical probing, which holds potential for the development of chip‐integrated OPMs as well as other advanced atomic devices where the integration of optical probing system is expected.