Clément CARLÉ :Microwave atomic clock with improved microcell technology and pulsed interrogation regime

Abstract :This PhD thesis work aims to propose innovative scientific and technological solutions for the demonstration a microcell-based CPT atomic clock with improved long-term frequency stability.

The first research axis has concerned the implementation of pulsed interrogation sequences used to reduce light-shifts induced during the interaction between the atoms and the optical interrogation field. The use of an advanced sequence named Symmetric Auto-Balanced Ramsey (SABR) has in particular allowed a reduction of the clock frequency sensitivity to variations of the optical field by more than two orders of magnitude, benefiting to the frequency stability for integration times higher than 100 s.

A second research axis has led to the proof-of-concept and the development of a new alkali vapor microfabricated cell tehnology, based on hermetic laser-actuated break- and make-seals, combined with the use of low permeation glass substrates, for enhanced choice and reinforced control of the cell inner atmosphere. A reduction of the permeation rate by a factor higher than 1000 was demonstrated in cells filled with helium using aluminosilicate glass coupled with Al2O3 coatings. Studies for the development of cells using new buffer gas mixtures and working at high temperature (>90°C) have been undertaken.

Complementary results of these two research axis led to the demonstration of a CPT atomic clock using a Cs-Ne microcell with aluminosilicate glass and operating with the SABR interrogation sequence. The combination of these approaches, reinforced by additional active stabilization loops of some key experimental parameters, has led to a fractional frequency stability of 7x10-11 at 1 s and 1.4x10-12 at 105 s. These stabilities at one day are competitive with those of best microcell-based microwave clocks

Jury composition :

Rodolphe BOUDOT, Chargé de recherche, Université Bourgogne Franche-Comté, PhD Director

Gaetano MILETI, Professor, Université de Neuchâtel, Reporter

Arnaud LANDRAGIN, Directeur de recherche, SYRTE, Reporter

Vincent GIORDANO, Directeur de recherche, Université Bourgogne Franche-Comté, Reviewer

Ghaya BAILI, Ingénieure de recherche, Thales TRT, Reviewer

Nicolas PASSILLY, Chargé de recherche, Université Bourgogne Franche-Comté, PhD Co-director

Localization : SUPMICROTECH - ENSMM 26, rue de l'Épitaphe 25000 BESANCON - salle Amphithéâtre Jules Haag