Generation of a high purity microwave signal from a dual-frequency op-vecsel for cpt-based atomic clocks (orale)

The availability of small atomic clocks should greatly improve the mobility and robustness of, for example, satellite positioning system and high bitrate communication networks. In this context, coherent population trapping (CPT) is an interesting technique for the development of compact atomic references. It is based on the coupling of the two hyperfine ground states of an alkali atom, through excitation to a common atomic level, by two phase-coherent laser fields. We propose an innovating laser source for the production of such bifrequency field based on the dual-frequency and dual-polarization operation of an optically-pumped vertical external-cavity semiconductor laser (OP-VECSEL). Laser noise contributions to clock performance have been evaluated and results in an estimated clock frequency stability of 2.7 x 10-12 over a second limited by laser intensity noise. Stability level below 3 x 10-13 over one second is reasonably reachable with small changes in clock working conditions or laser set-up.