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DÉVELOPPEMENT D'UNE HORLOGE A PIÉGEAGE
COHÉRENT DE POPULATION. ÉTUDE THÉORIQUE ET EXPÉRIMENTALE DU RÉGIME
IMPULSIONNEL ET CONTINU

Abstract : We have developed a new method of pulsed interrogation of an atomic transition based on coherent population trapping. In contrast to CPT interrogation in a continuous wave excitation, we show that the pulsed method leads to narrow fringes scaling as 1/2T where T is the duration between pulses. As each pulse serves for the creation and detection of the atomic coherence, this technique allows us to realise Raman-Ramsey or Dark Resonance fringes without any initial atomic preparation. The theoretic predictions are verified experimentally using thermal Cs atoms in a buffer gas cell. Two phase-locked lasers tuned near the optical transitions of Cs D1 line induce a coupling between the two hyperfine ground states. Pulsing the laser light probes the 9.2 GHz clock transition similarly to Ramsey interrogation. The narrowest observed fringe width is around 60 Hz limited in resolution by atomic collisions with the buffer gas. When a hyperfine relaxation of the coherence between the clock states is introduced, a slight shift occurs. Finally, the CPT pulse train is proposed to eliminate any dead time between each interrogation cycle of the clock transition. In summary, our method achieves high resolution spectroscopy with separated CPT fields in order to dilute systematic frequency shifts over the free evolution time T. This also eliminates power broadening of the clock transition which will always appear for continuous excitation. Our model includes external frequency shifts with a density matrix formalism combining precision measurements and quantum optics. Pulse sequences are designed that mix coherent steady states and optical transient nutations with a free evolution time of a ground state coherence. Armed with a set of EIT/Raman Bloch-like equations of motion to describe general composite pulses, dynamical solutions can be used for transient experiments requiring such preparation of coherent states. Phase shifts of internal atomic wave functions can be controlled to engineer a robust coherence while minimizing ac Stark shifts. Atomic states are manipulated via a time resolved detection by monitoring fluorescence, absorption or population transfer. As we shall show, the sensitivity to be expected from detection of such transients is often comparable and in some cases superior to that obtainable from steady state interrogation.
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https://tel.archives-ouvertes.fr/tel-00123499
Contributor : Thomas Zanon-Willette <>
Submitted on : Tuesday, January 9, 2007 - 7:41:09 PM
Last modification on : Monday, December 14, 2020 - 9:52:14 AM
Long-term archiving on: : Friday, November 25, 2016 - 2:07:42 PM

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  • HAL Id : tel-00123499, version 1

Citation

Thomas Zanon-Willette. DÉVELOPPEMENT D'UNE HORLOGE A PIÉGEAGE
COHÉRENT DE POPULATION. ÉTUDE THÉORIQUE ET EXPÉRIMENTALE DU RÉGIME
IMPULSIONNEL ET CONTINU. Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 2005. Français. ⟨tel-00123499⟩

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