Additive Manufacturing of functionalised atomic vapour cells for next-generation quantum technologies

Atomic vapour cells are an indispensable tool for quantum technologies (QT), but potential improvements are limited by the capacities of conventional manufacturing methods. Using an additive manufacturing (AM) technique - vat polymerisation by digital light processing - we demonstrate, for the first time, a 3D-printed glass vapour cell. The exploitation of AM capacities allows intricate internal architectures, overprinting of 2D optoelectronical materials to create integrated sensors and surface functionalisation, while also showing the ability to tailor the optical properties of the AM glass by in-situ growth of gold nanoparticles. The produced cells achieve ultra-high vacuum of $2 \times 10^{-9}$ mbar and enable Doppler-free spectroscopy; we demonstrate laser frequency stabilisation as a QT application. These results highlight the transformative role that AM can play for QT in enabling compact, optimised and integrated multi-material components and devices.

💡 Research Summary

This paper presents the first demonstration of a three‑dimensional printed glass atomic vapor cell fabricated by additive manufacturing (AM) using digital light processing (DLP) vat polymerisation. The authors formulate a high‑loading silica nanoparticle resin (≈50 wt % fumed silica, 40 nm average size) dispersed in a mixture of 2‑hydroxyethyl methacrylate (HEMA), tetra‑ethylene glycol diacrylate (TEGDA) and phenoxyethanol (POE). The resin exhibits a viscosity of 297 mPa·s at 1000 s⁻¹, suitable for DLP exposure. Optimised printing parameters (6.5 s exposure per layer, 45 mW cm⁻² intensity, 0.035 wt % photo‑absorber) achieve a curing depth that faithfully reproduces the CAD geometry. Light‑scattering simulations confirm that, despite anisotropic scattering from the silica particles, the overall polymerisation remains isotropic.

After printing, a washing and post‑cure step removes uncured resin, followed by a gradual thermal debinding that releases internal stresses without cracking. The brown “debonded” part is then sintered in an inert argon atmosphere at 1150 °C for 12 h, allowing the silica particles to fuse into a dense, amorphous glass (density 2.2 g cm⁻³). X‑ray diffraction and SEM confirm the lack of crystallinity and porosity. The process yields a linear shrinkage of about 27 % (both horizontal and vertical), which is compensated for in the design stage. The final cell is a 1 cm³ cube with 1.5 mm walls and two pairs of parallel optical windows, enabling two orthogonal beams to pass with minimal distortion.

The printed cells are mounted on a UHV flange via an annealed copper tube and achieve pressures down to 2 × 10⁻⁹ mbar, maintaining this level throughout the experiments and surviving temperatures up to 150 °C. Rubidium (⁸⁵Rb and ⁸⁷Rb) vapor is introduced, and single‑pass absorption spectroscopy at 780 nm shows >90 % transmission and clear Voigt profiles. Doppler‑free saturated absorption spectroscopy resolves hyperfine components of both isotopes, demonstrating the cell’s suitability for high‑resolution spectroscopy.

Laser frequency stabilisation is performed by locking a diode laser to the 85Rb F = 3 → F′ = 3×4 crossover transition. The error signal, obtained by modulating the laser current at 100 kHz and demodulating the photodiode output, feeds back to the laser driver. Allan deviation analysis shows a fractional frequency stability of ΔF/F ≈ 2 × 10⁻¹⁰ at 1 s, representing a 1–2 order‑of‑magnitude improvement over a free‑running laser and comparable performance to a conventional 75 mm glass cell when normalised to optical path length.

Beyond the basic cell, the authors exploit AM’s design freedom to create interconnected cells with variable‑length channels, and to over‑print conductive materials directly onto the glass. Gold nanoparticle (AuNP) doping is achieved by adding AuCl₃ to the resin; a photothermal reduction during sintering forms AuNPs in situ, tuning the visible‑range absorption of the glass. Ink‑jet printed graphene tracks on AuNP‑doped glass exhibit photoconductivity, with resistance decreasing under 550 nm illumination, demonstrating integrated photodetector functionality.

The work shows that DLP‑based AM can produce ultra‑high‑vacuum‑compatible glass components with complex internal geometries, multi‑material integration, and tunable optical properties—capabilities not attainable with traditional glass blowing or MEMS fabrication. Such printed vapor cells open pathways to compact, customisable quantum‑technology platforms, including miniaturised atomic clocks, magnetometers with built‑in shielding and detectors, and other sensor modules where size, shape, and functionality can be tailored on demand. Future developments may incorporate higher‑temperature materials, on‑chip electronics, and scalable production for widespread quantum‑technology deployment.