Saturated absorption spectroscopy of the near-UV Cs atom 6S1/2-7P1/2 transition in a MEMS vapor cell
Résumé
Microfabricated (MEMS) alkali vapor cells are at the core of high-precision integrated atomic quantum sensors and devices, such as microwave and optical clocks, or magnetometers. The first chip-scale atomic device was a microwave atomic clock based on coherent population trapping. It has offered in its industrial and commercialized version an ultra-low size-power-instability budget, impacting a plethora of industrial and scientific applications. Nevertheless, the short-term stability of these clocks is usually limited at about 10−10 at 1 s. Hot vapor MEMS-based optical frequency standards constitute a new generation of miniaturized clocks, with enhanced stability. These references keep the benefit of using wafer-scalable and mass-producible vapor cells while preventing ultra-high vacuum technologies and laser cooling. Among the transitions explored, the 6S1/2 − 7P1/2 near-UV transition of Cs atom was used to demonstrate an optical reference with a stability of 2.1 × 10−13 at 1 s and averaging down to a few 10−14. However, this reference was based on a 5 cm-long glass-blown cell, not compliant with the advent of a fullyminiaturized and low-power optical clock. In this work, we present the characterization of sub-Doppler resonances detected in a microfabricated cell by probing, in a simple saturated absorption configuration, the Cs atom 6S1/2 – 7P1/2 transition at 459 nm. The impact of the laser intensity and cell temperature on the sub-Doppler resonance is experimentally investigated. Optimal values are identified for the development of a near-UV microcell-stabilized frequency reference. Detection noise measurements are also reported, predicting a short-term stability in the 10−13 range at 1 s. Tests of cells with embedded getters are under progress for improved purity of the cell inner atmosphere and narrowing of the resonance. Latest results will be presented at the conference.
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