The most appealing features of chip-scale quantum sensors are their capability to maintain extreme sensitivity while enabling large-scale batch manufacturing. This necessitates high-level integration and wafer-level fabrication of atomic vapor cells. In this paper, we describe a micromachining paradigm for wafer-level atomic vapor cells functionalized by CMOS-compatible non-magnetic heaters and temperature sensors and demonstrate several innovative applications. Leveraging standard micro-nanofabrication technology, the integrated vapor cells achieved an ultra-long optical access of 5 mm, nearly four time that of previously microfabricated vapor cells. The feasibility of the integrated atomic vapor cells fabrication process was verified by a consecutive 30-day aging test in a harsh environment (operating temperature of 473 K and vacuum of approximately 1 Pa). Benefiting from the ultra-long optical path, we observed several typical quantum effects, including the saturation absorption and spin fluctuations, a regime previously inaccessible with conventional micromachined vapor cells. Finally, a zero-field quantum magnetometry with an ultra-high magnetic sensitivity of 12 fT/Hz1/2 was also demonstrated. Our achievements broaden the potential applications of microfabricated atomic vapor cells and pave the way for scalable manufacturing of ultrasensitive, chip-scale quantum sensors.
The most appealing features of chip-scale quantum sensors are their capability to maintain extreme sensitivity while enabling large-scale batch manufacturing. This necessitates high-level integration and wafer-level fabrication of atomic vapor cells. In this paper, we describe a micromachining paradigm for wafer-level atomic vapor cells functionalized by CMOS-compatible non-magnetic heaters and temperature sensors and demonstrate several innovative applications. Leveraging standard micro-nanofabrication technology, the integrated vapor cells achieved an ultra-long optical access of 5 mm, nearly four time that of previously microfabricated vapor cells. The feasibility of the integrated atomic vapor cells fabrication process was verified by a consecutive 30-day aging test in a harsh environment (operating temperature of 473 K and vacuum of approximately 1 Pa). Benefiting from the ultra-long optical path, we observed several typical quantum effects, including the saturation absorption and spin fluctuations, a regime previously inaccessible with conventional micromachined vapor cells. Finally, a zero-field quantum magnetometry with an ultra-high magnetic sensitivity of 12 fT/Hz1/2 was also demonstrated. Our achievements broaden the potential applications of microfabricated atomic vapor cells and pave the way for scalable manufacturing of ultrasensitive, chip-scale quantum sensors.
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.
We investigate the architecture of microfabricated vapor cells with reflective sidewalls for applications in chip scale atomic sensors. The optical configuration in operation is suitable for both one-beam and two-beam (pump & probe) schemes. In the miniaturized vapor cells, the laser beam is reflected twice by the aluminum reflectors on the wet etched 54.7° sidewalls to prolong the optical length significantly, thus resulting in a return reflectance that is three times that of bare silicon sidewalls. To avoid limitations faced in the fabrication process, a simpler, more universal and less constrained fabrication process of microfabricated vapor cells for chip scale atomic sensors with uncompromised performance is implemented, which also decreases the fabrication costs and procedures. Characterization measurements show that with effective sidewall reflectors, mm³ level volume and feasible hermeticity, the elongated miniature vapor cells demonstrate a linear absorption contrast improvement by 10 times over the conventional micro-electro-mechanical system (MEMS) vapor cells at ~50 °C in the rubidium D1 absorption spectroscopy experiments. At the operating temperature of ~90 °C for chip scale atomic sensors, a 50% linear absorption contrast enhancement is obtained with the reflective cell architecture. This leads to a potential improvement in the clock stability and magnetometer sensitivity. Besides, the coherent population trapping spectroscopy is applied to characterize the microfabricated vacuum cells with 46.3 kHz linewidth in the through cell configuration, demonstrating the effectiveness in chip scale atomic sensors.
Quantum sensing is an ever-evolving research field describing the use of a quantum phenomenon to perform measurement of a physical quantity. Amongst different types of quantum sensors, atomic vapor-based quantum effects are extensively used to measure quantities such as time, velocity, acceleration, electric, and magnetic fields. Here, we propose and demonstrate remote quantum sensing using a chip-scale atomic vapor cell. Specifically, we remotely interrogate millimeter-scale micromachined vapor cells, and measure the ambient Earth’s magnetic field at a standoff distance of ∼10 m and a sensitivity of ∼1 pT/√Hz. We further spatially map different magnetic fields in the presence of a noisy ambient environment. Simultaneously we are able measure the distance between a micro-cell and the interrogating system by means of time-of-flight measurements, thus correlating between position and magnetic field. Utilizing micromachined vapor cells for remote magnetometry offers substantial advantages in scalability, planar photonic integration, cost, and size. Consequently, we provide a novel toolset to deploy, measure, and map arbitrary, remote, and hard-to-access magnetic fields in unshielded environments with high sensitivity and spatial resolution, paving the way to a variety of novel applications in diverse fields such as medicine, communication, defense, space-exploration, and quantum technologies.
Atom-based technologies have played a central role in both fundamental research and application-driven developments. For example, devices such as atomic clocks and magnetometers are essential for precision time-keeping, navigation, and sensing. However, many of these demonstrations remain confined to laboratory settings due to their reliance on bulky equipment and centimeter-scale atomic vapor cells. In recent years, significant efforts have been made to miniaturize these vapor cells to enable field-deployable systems. Yet, integrating these cells with the necessary photonic components remains a complex and non-scalable process. To address this challenge, we have introduced the atomic-cladded waveguide (ACWG) architecture, which enables the integration of atomic and photonic functions on the same chip. While the ACWG concept provides a significant step forward toward integration, there is still a significant gap related to wafer scale manufacturability. In particular, previous demonstrations of atomic-photonic integration have relied on manual assembly of vapor cells onto single chips, restricting miniaturization, manufacturability, and thermal robustness. To revolutionize manufacturability of these devices, we hereby demonstrate our new generation of ACWG devices that overcomes these constraints. The approach is based on wafer bonding of a silicon wafer - consisting of multiple photonic chips to a glass wafer with pre-etched atomic chambers. This wafer-scale process yields multiple miniaturized integrated photonic-atomic chips in a single batch. The bonded devices operate reliably at elevated temperatures over an extended period of time, allowing higher atomic densities to be used. The fabrication method consists of well-defined, repeatable steps, paving the way for scalable production of mature integrated photonic-atomic systems for next-generation sensing, metrology, and quantum technologies, inspired by commercial complementary metal-oxide-semiconductor-based processes.
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.
Atomic magnetometers, a prominent class of quantum sensors, have become increasingly significant in magnetometry, with extensive applications in cutting-edge physics, biomedical imaging, industrial inspection, and beyond. However, the power consumption of an atomic magnetometer is primarily dominated by that demanded to heat the atomic vapor cell to its operating temperature. This operating temperature determines the alkali-metal atomic density, thereby influencing the magnetic field sensitivity and overall power consumption, which poses a potential obstacle to the large-scale engineering application of atomic magnetometers. In this article, a novel heating method utilizing renewable solar energy is proposed for the first time, which can surpass the limitation of conventional heating methods in thermo-atom-based quantum sensors. By exploiting an intelligent closed-loop control system to adaptively regulate the functionalized sunlight power, this proposed method has the capability of both high heating efficiency and accuracy. The heating properties and laser absorption spectrum at different temperatures up to 180 °C are characterized substantiating the feasibility of utilizing sunlight. Moreover, a sunlight-heated, highly sensitive, microfabricated atomic magnetometer with a magnetic field sensitivity of 18 fT/Hz1/2is demonstrated. And the single-chamber microelectromechanical system atomic vapor cell as the key component is fabricated by utilizing deep silicon micromachining and anodic bonding techniques. This proposed technique can be further extended to all quantum sensing systems based on thermal atomic ensembles and open up new possibilities for the development of self-powered, environmentally friendly quantum sensors.