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arXiv:2602.00390

Wafer-Scale Micro-Knife Sealed Vacuum Cells for Quantum Devices

Megan Kelleher, Konrad Ziegler, Jeremy Robin, Lianxin Huang, Mitchel Button, Liam Mauck, Judith Olson, Peter D. Brewer, Danny M. Kim, John E. Kitching, Ruwan Senaratne, William McGehee, Travis M. Autry

Published Jan 30, 2026• 0 citations
arXivHTMLPDF

Abstract

Advanced integration technologies greatly enhance the prospects and reliability of practical quantum sensors, atomic clocks, and quantum information technologies. The performance and proliferation of these devices at chip-scale is contingent upon developing low leak and low gas permeation vacuum cells using wafer-scale techniques. Here we demonstrate both evacuated atomic beam cells and atomic vapor cells using plastic deformation micro-knife bonding of selectively etched fused silica wafers. The cells are characterized using saturated absorption spectroscopy and fluorescence measurements. Vapor cells are mechanically robust exhibiting sheer-force strength ($\sim 15$MPa), demonstrate long lifetimes ($> 1$ year), low residual gas pressures $ (\ll 10^{-3} \, \text{mbar}) $, and leak rates below fine-leak testing sensitivity ($\ll 2.8 \times 10^{-10} \frac{\text{mBar} \cdot \text{L}}{\text{s}}$). Micro-knife bonding greatly simplifies the fabrication process for complex chip scale atom-beam devices and atomic vapor cells while identifying a path to future chip-scale cold atom devices, improved chip scale atomic clocks, and fieldable dissipation-dilution-limited optomechanics.

DOI
10.48550/arxiv.2602.00390

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Advanced integration technologies greatly enhance the prospects and reliability of practical quantum sensors, atomic clocks, and quantum information technologies. The performance and proliferation of these devices at chip-scale is contingent upon developing low leak and low gas permeation vacuum cells using wafer-scale techniques. Here we demonstrate both evacuated atomic beam cells and atomic vapor cells using plastic deformation micro-knife bonding of selectively etched fused silica wafers. The cells are characterized using saturated absorption spectroscopy and fluorescence measurements. Vapor cells are mechanically robust exhibiting sheer-force strength (∼15\sim 15∼15MPa), demonstrate long lifetimes (>1> 1>1 year), low residual gas pressures (≪10−3 mbar)(\ll 10^{-3} \, \text{mbar})(≪10−3mbar), and leak rates below fine-leak testing sensitivity (≪2.8×10−10mBar⋅Ls\ll 2.8 \times 10^{-10} \frac{\text{mBar} \cdot \text{L}}{\text{s}}≪2.8×10−10smBar⋅L​). Micro-knife bonding greatly simplifies the fabrication process for complex chip scale atom-beam devices and atomic vapor cells while identifying a path to future chip-scale cold atom devices, improved chip scale atomic clocks, and fieldable dissipation-dilution-limited optomechanics.
Abstract Advanced integration technologies greatly enhance the prospects and reliability of practical quantum sensors, atomic clocks, and quantum information technologies. The performance and proliferation of these devices at chip scale is contingent upon developing low leak and low gas permeation vacuum cells using wafer-scale techniques. Here, we demonstrate a novel, low-leak-rate micro-knife bonding approach, enabling the realization of both atomic vapor cells and more complex evacuated atomic beam devices. These devices are fabricated using selective laser etching in a fused silica platform. The vapor cells are mechanically robust exhibiting shear-force strength ∼ 15 MPa, demonstrate long lifetimes ( > 1 year), low residual gas pressures ( ≪ 10 − 3 mbar ) , and leak rates below fine-leak testing sensitivity ( ≪ 2.8 × 10 − 10 mbar ⋅ l s − 1 ). Micro-knife bonding greatly simplifies the fabrication process for complex chip scale atom-beam devices and atomic vapor cells while identifying a path to future chip-scale cold atom devices, improved chip scale atomic clocks, and fieldable dissipation-dilution-limited optomechanics.
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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.
We describe a process for fabricating a wafer-scale array of alkali metal vapor cells with low residual gas pressure. We show that by etching long, thin channels between the cells on the Si wafer surface, the residual gas pressure in the evacuated vapor cell can be reduced to below 0.5 kPa (4 Torr) with a yield above 50%. The low residual gas pressure in these mass-producible alkali vapor cells can enable a new generation of low-cost chip-scale atomic devices such as vapor cell optical clocks, wavelength references, and Rydberg sensors.
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.