Characterization of compact CPT clocks based on a Cs-Ne microcell

This paper reports the characterization of compact Cs CPT clocks based on a single buffer gas Cs-Ne microcell. Two different experimental set-ups are tested. The first set-up uses an externally-modulated 895 nm Distributed Feedback (DFB) laser source while the second one uses a directly-modulated custom-designed 895 nm Vertical Cavity Surface Emitting Laser (VCSEL) source. Using the DFB set-up, through reduction of the temperature-dependent collisional frequency shift and an active light shift suppression technique, a clock frequency stability of 3.8 × 10^-11 at 1 s and greatly better than 10^-11 at 60000 s is demonstrated. This proves the potential of single buffer gas Cs-Ne microfabricated cells for the development of miniature atomic clocks. Preliminar characterization of CPT resonances are reported with the VCSEL-based setup. It is expected that similar clock stability performances are achievable in this case.