A significant drive has emerged to miniaturize and integrate atomic magnetometers for various ultra-high precision quantum sensing applications, extending from laboratory research to industrial use. We introduce a novel configuration of a single-beam atomic magnetometer based on space division multiplexing (SDM), offering a promising approach to this field of research. This design utilizes a custom-designed metasurface to manipulate two generated modes, enabling the implementation of a pump-probe configuration within a single-beam atomic magnetometer. This approach achieves higher spatial resolution and reduces the system's volume. The metasurface centrally generates circularly polarized light carrying spin angular momentum, while linearly polarized light is emitted from the outer areas. This design not only enhances the miniaturization of chip-scale atomic magnetometers but also opens new avenues for exploring interactions between hot atomic spin ensembles and vector beams.
A significant drive has emerged to miniaturize and integrate atomic magnetometers for various ultra-high precision quantum sensing applications, extending from laboratory research to industrial use. We introduce a novel configuration of a single-beam atomic magnetometer based on space division multiplexing (SDM), offering a promising approach to this field of research. This design utilizes a custom-designed metasurface to manipulate two generated modes, enabling the implementation of a pump-probe configuration within a single-beam atomic magnetometer. This approach achieves higher spatial resolution and reduces the system's volume. The metasurface centrally generates circularly polarized light carrying spin angular momentum, while linearly polarized light is emitted from the outer areas. This design not only enhances the miniaturization of chip-scale atomic magnetometers but also opens new avenues for exploring interactions between hot atomic spin ensembles and vector beams.
Emerging atomic magnetometers (AMs) are among the most advanced sensors for detecting and characterizing magnetic fields. Recently, there has been growing interest in the miniaturization and integration of AMs due to the urgent demand for portability and compactness in various fields such as biomagnetism imaging. While conventional AMs require a bulky setup of optical devices for the pumping and optical readout of atomic spin, here, a novel chip-scale single-beam AM scheme is proposed by leveraging extreme transmissive circular polarization dichroism (TCPD) and geometric phase manipulation of spin-selective interference meta-optics. This is achieved through silicon-based metasurfaces that enable the realization of arbitrary-to-circular polarization conversion and wavefront modulation within a monolithic chip at Rb D1 transition wavelength (λ = 795 nm). Two spin-selective interference metasurfaces, i.e., meta-circular-polarizer (MCP) and meta-circular-polarizer-lens (MCPL), are fabricated and characterized, with a measured TCPD of 0.68 for the MCP as well as focusing efficiency and TCPD of around 70.67% and 0.69 for the MCPL, respectively. As a proof of concept, a 4 × 4 × 4 mm 3 Rb vapor cell is combined with our metasurface to construct a miniaturized single-beam AM. The sensitivity of our compact metasurface-based system is about 15 fT/Hz 1/2, with a dynamic range near zero-field of ± 2.2 nT. We envision that this work could facilitate the development of burgeoning chip-scale quantum sensors, which hold great potential for high-spatial-resolution biomagnetic imaging, on-chip nuclear magnetic resonance, and so forth.
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.
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.
Atomic magnetometers with magnetic field modulation have emerged as pivotal sensors for biomagnetic measurements. However, challenges such as crosstalk between adjacent modulation fields and the complexity of signal circuitry become increasingly serious in the development of array-based equipment with the magnetometers, especially in the miniaturized atomic magnetometer. This paper proposes an all-optical, fully integrated fiber-coupled atomic magnetometer that employs pump beam modulation. A miniaturized atomic magnetometer with a volume of 10 cm³ has been designed, incorporating an active measurement area of 3 × 3 × 3 mm3. The magnetometer operates in the spinexchange relaxation-free (SERF) regime with an 87Rb vapor cell. An amplitude-modulated pump beam directly modulates the rubidium atomic ensembles, rather than the magnetic field modulation. The optical rotation angle is detected by an unmodulated probe beam oriented orthogonally to the pump beam. In light of the discontinuous pumping characteristics, we developed a modified theoretical model to clarify the output response of the proposed atomic magnetometer. The experimental results demonstrate that the new design achieves the same sensitivity as conventional magnetometer configurations with a smaller volume and without crosstalk of the magnetic field. This research highlights the significant potential for advancing the development of highly sensitive, miniaturized atomic magnetometers, making them particularly suitable for applications in magnetocardiography (MCG) and magnetoencephalography (MEG).
We demonstrate atomic magnetometry using a metasurface polarizing beamsplitter fabricated on a silicon-on-sapphire (SOS) platform. The metasurface splits a beam that is near-resonant with the rubidium atoms (795 nm) into orthogonal linear polarizations, enabling the measurement of magnetically sensitive circular birefringence in rubidium vapor through balanced polarimetry. We incorporated the metasurface into an atomic magnetometer based on nonlinear magneto-optical rotation and measured subnanotesla sensitivity, which is limited by low-frequency technical noise and transmission loss through the metasurface. To our knowledge, this work represents the first demonstration of SOS nanophotonics for atom-based sensing and paves the way for highly integrated, miniaturized atomic sensors with enhanced sensitivity and portability.
Atomic magnetometry is one of the most sensitive field-measurement techniques for biological, geo-surveying, and navigational applications. An essential process in atomic magnetometry is measurement of optical polarization rotation of a near-resonant beam due to its interaction with atomic spins under an external magnetic field. In this work, we present the design and analysis of a silicon-metasurface-based polarization beam splitter that have been tailored for operation in a rubidium magnetometer. The metasurface polarization beam splitter operates at a wavelength of 795 nm and has a transmission efficiency > 83% and a polarization extinction ratio > 20 dB. We show that these performance specifications are compatible with magnetometer operation in miniaturized vapor cells with sub-picotesla-level sensitivity and discuss the prospect of realizing compact, high-sensitivity atomic magnetometers with nanophotonic component integration.