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Lasers ultra-stables asservis sur trous-brûlés spectraux ; développement en vue d'une application aux horloges optiques

Abstract : Optical lattice clocks show impressive performances and are begining to raise the question of the redefinition of the SI second. In these systems, an ultra-stable laser is used as local oscillator to probe very narrow optical transitions of neutral atoms trapped in an optical lattice. The ultime stability of these systems, determined by the number of atoms interrogated at each clock cycle, evaluated at a few 10^-17/sqrt(tau) (where tau is the integration time), is currently not reached and is limited to a few 10^-16/sqrt(tau) by the phase fluctuations of the probe laser. If the enhancement of the ultra stable cavities, on which are currently stabilized the probe lasers, is widely studied, LNE-SYRTE has adopted a more recent approach where the frequency reference is a spectral hole burned in rare earth doped crystal cooled down at cryogenic temperature (around 4 K). A short term stability of a few 10^-18 could be achieved. This thesis describes the construction of the experiment and present the results of a high resolution spectroscopy of narrow spectral holes (FWHM = 3.3 kHz) burned in the crystal Eu3+ :Y2SiO5. The influence of the closed cycle cryostat on the behaviour of the spectral holes is hightlighted and reduced. Finally, an original locking scheme based on a heterodyne detection of a spectral hole and a numerical lock program using FPGA in order to stabilize the laser frequency on the top of the narrow spectral hole is described and shows a short term stability of a few 10^-14, which is a first promising result for the future of the project.
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Contributor : Olivier Gobron <>
Submitted on : Monday, April 3, 2017 - 10:08:30 PM
Last modification on : Monday, December 14, 2020 - 9:45:56 AM
Long-term archiving on: : Tuesday, July 4, 2017 - 2:57:00 PM

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  • HAL Id : tel-01501185, version 1

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Olivier Gobron. Lasers ultra-stables asservis sur trous-brûlés spectraux ; développement en vue d'une application aux horloges optiques. Physique [physics]. Université Pierre et Marie Curie, 2017. Français. ⟨tel-01501185⟩

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