MEMS cell for compact two-photon optical clock

Balet, L.; Torchebœuf, N.; Voumard, T.; Miran Zadeh, T.; Overstolz, T.; Haesler, J.; Karlen, S.

MEMS cell for compact two-photon optical clock

Author

Balet, L.

Torchebœuf, N.

Voumard, T.

Miran Zadeh, T.

Overstolz, T.

Haesler, J.

Karlen, S.

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Abstract

We report on the development and characterization of MEMS-based rubidium vapor cells designed for compact two-photon optical clocks. The performance of such clocks depends critically on minimizing background gas pressure, which otherwise broadens the two-photon transition and limits frequency stability. To overcome the intrinsic nitrogen release associated with our historical RbN3-based filling method, we investigated alternative alkali-metal filling strategies compatible with wafer-level fabrication. We implemented a multi-cavity MEMS design using low-helium-permeation aluminosilicate glass (ASG) and evaluated several rubidium sources, including RbBi alloys, RbN3, and commercial rubidium dispensers (Rb micropills) coupled with non-evaporable getters (NEG). Two-photon interrogation of the 87Rb Fg = 2 → Fe = 1 to 4 transitions yielded a 600 kHz linewidth, close to the theoretical limit, demonstrating good suitability for compact optical-clock applications.