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Developments for miniature atomic magnetometry

Linda Péroux

Published Mar 16, 2026• 0 citations

Abstract

Sensitive and accurate magnetic-field measurements are essential in many applications, including geophysical studies, biomagnetic signal detection, navigation, event monitoring, and magnetic anomaly detection. In this context, atomic magnetometers are a particularly promising approach, combining high sensitivity and accuracy, and able to rival superconducting quantum interference devices (SQUIDs) without requiring cryogenic cooling. While the best sensitivity levels are achieved in the zero-field regime within magnetic shielding, scalar magnetometers operating in ambient fields also demonstrated remarkable sensitivities. Initiated in the 2000s, the miniaturization of atomic devices, and in particular alkali-vapor cells, paves the way for magnetometers that are both sensitive and compact, well suited to embedded measurements and field applications.This thesis contributes to the development of microfabricated vapor cells for atomic magnetometry. We propose a new filling and sealing method that overcomes some limitations of conventional approaches and could enable the fabrication of purer cells compatible with a wider range of chemical species. This strategy could also facilitate the integration of anti-relaxation coatings, which reduce relaxation caused by collisions with the cell walls. To date, no long-lasting anti-relaxation effects have been demonstrated in microfabricated cells, as traditional methods rely on high temperatures that are incompatible with these coatings.A cell design suited to the deposition of anti-relaxation coatings is presented. We then describe the fabrication and characterization of a multi-axis microfabricated cell, designed for compact atomic devices using multiple optical beams. This multi-axis cell was experimentally validated in a dual-beam magnetometry configuration using an experimental setup developed as part of this thesis.

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Abstract Microfabricated alkali vapor cells enable the miniaturization of atomic sensors, but require collective wafer-level integration of complex features. In many applications-including magnetometers, gyroscopes, magneto-optical traps, and fluorescence imaging-multiple optical accesses are needed to enhance performance. Yet, achieving this without compromising manufacturability remains challenging. In this work, we present a wafer-level fabrication approach that enables three orthogonal optical pathways in microfabricated alkali vapor cells, using fully scalable and collective processes. Our method relies on the thermal reflow of glass preforms, shaped by laser-assisted etching (LAE) and bonded between silicon frames. The relatively low surface roughness produced by LAE allows for effective reflow, which further smooths the surfaces without significantly compromising the optical planarity of the windows. This process results in multi-axis vapor cells featuring embedded, optics-grade lateral windows. We evaluate the device performance through both single-beam and dual-beam atomic magnetometry measurements. Magnetic sensitivities better than 200 fT Hz − 1 are demonstrated along each of the three orthogonal axes, confirming the potential of the approach for tri-axis magnetic field sensing at sub-picotesla resolution. This fabrication strategy opens new perspectives for versatile, high-performance atomic sensors, fully compatible with wafer-level integration and mass production.

arXiv:2509.22456•Journal of Physics Photonics•Dec 2, 2025•1 citation

Characterization of 87Rb MEMS vapor cells for miniature atomic magnetometers

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Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the 87Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the 87Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the 87Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments.

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Micro-fabriced alkali vapor cells and applications in various fields as the heart of ultraprecise sensors, like chip scale atomic clocks, magnetometers or gyroscopes. Miniaturization asks for either new fabrication techniques or new physical concepts or both. We present here a new fabrication technique for the alkali cells which allows the integration of a anti-relaxation wall coating for alkali vapor cells in order to improve the signal for miniazurized cells.

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Compared with superconducting quantum interference devices, chip-scale atomic magnetometers using the wafer-level micro alkali vapor cells can be used more conveniently in the applications of geophysical mapping, health care and remote monitoring. Drastic wall collisions and decreased polarization lifetime are the main barriers for the performance of the chip-scale atomic magnetometers. In this study, OTS organic films coated on the inner surface of the micro vapor cells were used to suppress wall collisions and improve polarization lifetime of the alkali atoms in the micro cells. First of all, the fabrication process of wafer-level micro OTS coated vapor cells is introduced, the process is based on anodic bonding technology. Then the prepared wafer-level micro OTS coated vapor cells have been characterized by the water-contact angle test and measured in the micro-machined spin-exchange relaxation free(SERF) atomic magnetometers. Results show that the OTS coating is effective after anodic bonding from the water contact angle test. Results also indicate that the spin exchange relaxation free atomic magnetometer using the micro OTS-coated vapor cell can operate successfully.

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Abstract The chip-scale hybrid optical pumping spin-exchange relaxation-free (SERF) atomic magnetometer with a single-beam arrangement has prominent applications in biomagnetic measurements because of its outstanding features, including ultrahigh sensitivity, an enhanced signal-to-noise ratio, homogeneous spin polarization and a much simpler optical configuration than other devices. In this work, a miniaturized single-beam hybrid optical pumping SERF atomic magnetometer based on a microfabricated atomic vapor cell is demonstrated. Although the optically thin Cs atoms are spin-polarized, the dense Rb atoms determine the experimental results. The enhanced signal strength and narrowed resonance linewidth are experimentally proven, which shows the superiority of the proposed magnetometer scheme. By using a differential detection scheme, we effectively suppress optical noise with an approximate five-fold improvement. Moreover, the cell temperature markedly affects the performance of the magnetometer. We systematically investigate the effects of temperature on the magnetometer parameters. The theoretical basis for these effects is explained in detail. The developed miniaturized magnetometer has an optimal magnetic sensitivity of 20 fT/Hz 1/2 . The presented work provides a foundation for the chip-scale integration of ultrahighly sensitive quantum magnetometers that can be used for forward-looking magnetocardiography (MCG) and magnetoencephalography (MEG) applications.

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Research progress of chip-scale atomic vapor cells for atomic sensors

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High-sensitivity sensors play a critical role in fundamental physics research, space magnetic field detection, geological monitoring, and biomedical applications. Atomic sensors, based on quantum mechanics principles, such as atomic magnetometers, atomic clocks, and atomic gyroscopes, etc. have emerged as pivotal technical equipment for precision measurements due to their exceptional sensitivity, low power consumption, and long-term stability. The atomic vapor cell, serving as the core component, facilitates quantum state manipulation via the Zeeman effect. Miniaturization and integration of these cells have not only advanced the development of portable atomic magnetometers but also provided a foundation for breakthroughs in chip-scale atomic clocks and enhanced navigation accuracy of atomic gyroscopes. The research progresses of chip-scale atomic vapor cells in recent years are reviewed. The advancements in alkali metal introduction methods, anti-relaxation surface coatings, and micro-nano fabrication techniques have enabled the miniaturization of atomic vapor cells while preserving high performance, creating new opportunities for the deployment of quantum sensing technologies across diverse fields. Looking ahead, multifunctional integration and material innovations in atomic vapor cells are expected to further broaden their applications in time-frequency standards, inertial navigation systems, and weak magnetic field measurements.

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Sensitive and accurate magnetic-field measurements are essential in many applications, including geophysical studies, biomagnetic signal detection, navigation, event monitoring, and magnetic anomaly detection. In this context, atomic magnetometers are a particularly promising approach, combining high sensitivity and accuracy, and able to rival superconducting quantum interference devices (SQUIDs) without requiring cryogenic cooling. While the best sensitivity levels are achieved in the zero-field regime within magnetic shielding, scalar magnetometers operating in ambient fields also demonstrated remarkable sensitivities. Initiated in the 2000s, the miniaturization of atomic devices, and in particular alkali-vapor cells, paves the way for magnetometers that are both sensitive and compact, well suited to embedded measurements and field applications.This thesis contributes to the development of microfabricated vapor cells for atomic magnetometry. We propose a new filling and sealing method that overcomes some limitations of conventional approaches and could enable the fabrication of purer cells compatible with a wider range of chemical species. This strategy could also facilitate the integration of anti-relaxation coatings, which reduce relaxation caused by collisions with the cell walls. To date, no long-lasting anti-relaxation effects have been demonstrated in microfabricated cells, as traditional methods rely on high temperatures that are incompatible with these coatings.A cell design suited to the deposition of anti-relaxation coatings is presented. We then describe the fabrication and characterization of a multi-axis microfabricated cell, designed for compact atomic devices using multiple optical beams. This multi-axis cell was experimentally validated in a dual-beam magnetometry configuration using an experimental setup developed as part of this thesis.

Abstract Microfabricated alkali vapor cells enable the miniaturization of atomic sensors, but require collective wafer-level integration of complex features. In many applications-including magnetometers, gyroscopes, magneto-optical traps, and fluorescence imaging-multiple optical accesses are needed to enhance performance. Yet, achieving this without compromising manufacturability remains challenging. In this work, we present a wafer-level fabrication approach that enables three orthogonal optical pathways in microfabricated alkali vapor cells, using fully scalable and collective processes. Our method relies on the thermal reflow of glass preforms, shaped by laser-assisted etching (LAE) and bonded between silicon frames. The relatively low surface roughness produced by LAE allows for effective reflow, which further smooths the surfaces without significantly compromising the optical planarity of the windows. This process results in multi-axis vapor cells featuring embedded, optics-grade lateral windows. We evaluate the device performance through both single-beam and dual-beam atomic magnetometry measurements. Magnetic sensitivities better than 200 fT Hz − 1 are demonstrated along each of the three orthogonal axes, confirming the potential of the approach for tri-axis magnetic field sensing at sub-picotesla resolution. This fabrication strategy opens new perspectives for versatile, high-performance atomic sensors, fully compatible with wafer-level integration and mass production.

Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the 87Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the 87Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the 87Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments.

Compared with superconducting quantum interference devices, chip-scale atomic magnetometers using the wafer-level micro alkali vapor cells can be used more conveniently in the applications of geophysical mapping, health care and remote monitoring. Drastic wall collisions and decreased polarization lifetime are the main barriers for the performance of the chip-scale atomic magnetometers. In this study, OTS organic films coated on the inner surface of the micro vapor cells were used to suppress wall collisions and improve polarization lifetime of the alkali atoms in the micro cells. First of all, the fabrication process of wafer-level micro OTS coated vapor cells is introduced, the process is based on anodic bonding technology. Then the prepared wafer-level micro OTS coated vapor cells have been characterized by the water-contact angle test and measured in the micro-machined spin-exchange relaxation free(SERF) atomic magnetometers. Results show that the OTS coating is effective after anodic bonding from the water contact angle test. Results also indicate that the spin exchange relaxation free atomic magnetometer using the micro OTS-coated vapor cell can operate successfully.

Abstract The chip-scale hybrid optical pumping spin-exchange relaxation-free (SERF) atomic magnetometer with a single-beam arrangement has prominent applications in biomagnetic measurements because of its outstanding features, including ultrahigh sensitivity, an enhanced signal-to-noise ratio, homogeneous spin polarization and a much simpler optical configuration than other devices. In this work, a miniaturized single-beam hybrid optical pumping SERF atomic magnetometer based on a microfabricated atomic vapor cell is demonstrated. Although the optically thin Cs atoms are spin-polarized, the dense Rb atoms determine the experimental results. The enhanced signal strength and narrowed resonance linewidth are experimentally proven, which shows the superiority of the proposed magnetometer scheme. By using a differential detection scheme, we effectively suppress optical noise with an approximate five-fold improvement. Moreover, the cell temperature markedly affects the performance of the magnetometer. We systematically investigate the effects of temperature on the magnetometer parameters. The theoretical basis for these effects is explained in detail. The developed miniaturized magnetometer has an optimal magnetic sensitivity of 20 fT/Hz 1/2 . The presented work provides a foundation for the chip-scale integration of ultrahighly sensitive quantum magnetometers that can be used for forward-looking magnetocardiography (MCG) and magnetoencephalography (MEG) applications.

High-sensitivity sensors play a critical role in fundamental physics research, space magnetic field detection, geological monitoring, and biomedical applications. Atomic sensors, based on quantum mechanics principles, such as atomic magnetometers, atomic clocks, and atomic gyroscopes, etc. have emerged as pivotal technical equipment for precision measurements due to their exceptional sensitivity, low power consumption, and long-term stability. The atomic vapor cell, serving as the core component, facilitates quantum state manipulation via the Zeeman effect. Miniaturization and integration of these cells have not only advanced the development of portable atomic magnetometers but also provided a foundation for breakthroughs in chip-scale atomic clocks and enhanced navigation accuracy of atomic gyroscopes. The research progresses of chip-scale atomic vapor cells in recent years are reviewed. The advancements in alkali metal introduction methods, anti-relaxation surface coatings, and micro-nano fabrication techniques have enabled the miniaturization of atomic vapor cells while preserving high performance, creating new opportunities for the deployment of quantum sensing technologies across diverse fields. Looking ahead, multifunctional integration and material innovations in atomic vapor cells are expected to further broaden their applications in time-frequency standards, inertial navigation systems, and weak magnetic field measurements.