Compact atomic clock prototype based on coherent population trapping

¹ Laboratoire national de métrologie et d’essais – Systèmes de Référence Temps-Espace (LNE-SYRTE), Observatoire de Paris, CNRS UMR 8630, Université Pierre et Marie Curie, 61 Avenue de l’Observatoire, 75014, Paris, France
² present address: Laboratoire Commun de Métrologie LNE-CNAM, 61 rue du Landy, 93210, La Plaine Saint Denis, France

^a Corresponding author: jean-marie.danet@obspm.fr

Published online: 19 August 2014

Abstract

Toward the next generations of compact atomic clocks, clocks based on coherent population trapping (CPT) offer a very interesting alternative. Thanks to CPT, a quantum interfering process, this technology has made a decisive step in the miniaturization direction. Fractional frequency stability of 1.5x10^-10 at 1 s has been demonstrated in commercial devices of a few cm³. The laboratory prototype presented here intends to explore what could be the ultimate stability of a CPT based device. To do so, an original double-Λ optical scheme and a pulsed interrogation have been implemented in order to get a good compromise between contrast and linewidth. A study of two main sources of noise, the relative intensity and the local oscillator (LO) noise, has been performed. By designing simple solutions, it led to a new fractional frequency limitation lower than 4x10^-13 at 1 s integration. Such a performance proves that such a technology could rival with classical ones as double resonance clocks.