Thesis Dissertation Defense

Abstract: Atomic beams are a key technology for realizing navigation-grade timekeeping and inertial sensing instruments. Miniaturization of atom beam technology can enable new quantum sensor architectures benefitting from foundry production and microfabrication approaches. This thesis paves the way towards future atomic sensing devices using chip-scale thermal atomic beams enabled by MEMS (micro-electromechanical systems) technology in three steps – chip-scale atomic beam collimation, brightness enhancement, and vacuum packaging. We first demonstrated using a microfabricated thin capillary array to create highly collimated, continuous rubidium atom beams traveling parallel to a silicon wafer surface. Precise, lithographic definition of the guiding channels allowed us to shape and tailor atoms’ velocity distributions in ways not possible using conventional machining.

We then performed beam brightening via blue-detuned optical molasses following pre-collimation given by these microchannel arrays. Stimulated forces reduced the transverse velocity spread to below 1 m/s within a total travel distance of 4.5 mm upon a silicon substrate, consuming a cooling power of only 8 mW, 9 times lower power than earlier free-space experiments on cesium. Finally, we achieved a fully chip-scale atomic beam system containing an atom vapor reservoir and atomic beam drift region bridged by those thin silicon microchannels for differential pumping, in conjunction with graphite and non-evaporable getters embedded in the anodically bonded silicon-glass cell for sustaining the vacuum. In addition, we also performed free-space Ramsey interferometry with a two-zone separation as short as 8 mm, which mimicked the conditions and constraints for its future implementation on this chip-scale platform to unleash its potential in inertial sensing and timekeeping.

Reference:

Li, C., Chai, X., Wei, B., Yang, J., Daruwalla, A., Ayazi, F., & Raman, C. (2019). Cascaded collimator for atomic beams traveling in planar silicon devices. Nature communications, 10(1), 1-8.

Li, C., Wei, B., Chai, X., Yang, J., Daruwalla, A., Ayazi, F., & Raman, C. (2020). Robust characterization of microfabricated atomic beams on a six-month time scale. Physical Review Research, 2(2), 023239.

Wei, B., Crawford, A., Andeweg, Y., Zhuo, L., Li, C., & Raman, C. (2022). Collimated versatile atomic beam source with alkali dispensers. Appl. Phys. Lett. 120, 144001.

Li, C., Martinez, G., McGehee, W., Kitching, J., & Raman, C. (2022). A Microfabricated Chip-scale Atomic Beam System with Self-sustained Vacuum. Bulletin of the American Physical Society.