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arXiv:2509.22456 · Journal of Physics Photonics

Microfabricated multi-axis cell for integrated atomic devices

Linda Péroux, A. Dewilde, Andrei Mursa, Aurelien Mazzamurro, Jérémy Bonhomme, Quentin A. A. Tanguy, Emmanuel Klinger, Ludovic Gauthier‐Manuel, Olivier Gaiffe, Abdelkrim Talbi, Rodolphe Boudot, Philippe Pernod, J-F Clément, Vincent N. Maurice, Nicolas Passilly

Published Dec 2, 2025• 1 citation
arXivHTMLPDF

Abstract

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.

DOI
10.1088/2515-7647/ae2710

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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.
Existing microfabricated atomic vapor cells have only one optical channel, which is insufficient for supporting the multiple orthogonal beams required by atomic devices. In this study, we present a novel wafer-level manufacturing process for fabricating multi-optical-channel atomic vapor cells and an innovative method for batch processing the inner sidewalls of millimeter glass holes to meet optical channel requirements. Surface characterization and transmittance tests demonstrate that the processed inner sidewalls satisfy the criteria for an optical channel. In addition, the construction of an integrated processing platform enables multilayer non-isothermal anode bonding, the filling of inert gases, and the recovery and recycling of noble gases. Measurements of the absorption spectra and free-induction decay signals of xenon-129 (129Xe) and xenon-131 (131Xe) under different pump-probe schemes demonstrate the suitability of our vapor cell for use in atomic devices including atomic gyroscopes, dual-beam atomic magnetometers, and other optical/atomic devices. The proposed micromolding technology has broad application prospects in the field of optical-device processing.
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In this letter, we present a novel microfabricated shaped rubidium vapor cell with 3 cm optical path length for miniaturized atomic magnetometers. The novel shaped rubidium vapor cells are manufactured by a wafer-level fabrication process, and the process consists of the following three steps sequentially: first, wet etching to form oblong shallow cavity arrays; second, anodic bonding, glass reflowing, and wet etching to obtain a glass wafer with shaped structures; third, anodic bonding and chemical reaction to obtain the wafer-level shaped rubidium vapor cells. A miniaturized atomic magnetometer using the novel shaped rubidium vapor cell is characterized in the geomagnetic environment. The performance of the novel shaped rubidium vapor cell is compared with the traditional microfabricated rubidium vapor cell of a “glass–silicon–glass” sandwich structure. Results show that the measured geomagnetic field is 47.85 μT. It is demonstrated that the dispersive signal's slope of the novel shaped rubidium vapor cell is 15 times larger than that of the traditional one. Results also indicate that the miniaturized atomic magnetometer working in the geomagnetic environment has a magnetic noise spectral density of 3.5 pT/Hz1/2from 1 to 2 Hz.
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.
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.
Abstract We demonstrate a new technique for filling mm-scale microfabricated silicon and glass cavities with alkali vapors at the wafer-scale. A single etched silicon wafer contains an array of cavities containing alkali precursor materials offset laterally from the cell array. The wafer is heated to create an array of alkali droplets on an upper glass wafer, which is then translated laterally under vacuum and bonded to create the cells. This technique can be implemented in a commercially available bonding tool, allows the fabrication of cells with arbitrary buffer gas contents and pressures and can potentially produce cells with dimensions below 100 µm.