STAGE Offre de stage: Optical phase locked loop for time and frequency metrology

Date de mise à jour de l’offre

Laboratoire SYRTE Observatoire de Paris :

Alliant recherche de très haut niveau et services scientifiques, le SYRTE se place aujourd’hui au premier rang international dans des champs disciplinaires variés : métrologie du temps et des fréquences, systèmes de référence célestes, rotation de la Terre, histoire de l’astronomie. La pluridisciplinarité du SYRTE se retrouve aussi dans ses compétences transverses - théorie, instrumentation, traitement et analyse de données - et dans la diversité de ses objectifs qui vont de la physique fondamentale jusqu’au transfert industriel. Le SYRTE a des partenariats avec plusieurs organismes publics, dont notamment le CNES, la DGA, l’ESA, le Bureau International des Poids et Mesures (BIPM), et de nombreux industriels. Il est membre fondateur du Laboratoire d’Excellence du Programme Investissements d’Avenir FIRST-TF. Parallèlement à ses activités de recherche, le SYRTE assure des services nationaux et internationaux. Il compte en son sein le LNE-SYRTE.

Description de la mission

The future of time and frequency metrology lies in the optical domain : the second, the unit of time
will soon be defined via an optical transition in atoms ; optical clocks around the world have reported
unprecedented performance in both stability and accuracy ; and optical fiber networks provide
means of comparing distant clocks and disseminating frequency and time. In the heart of such
developments, an essential tool is the ultra-stable lasers.
Standard ultra-stable lasers nowadays derive their frequency stability from a Fabry-Perot cavity,
which has hit its fundamental stability limit since the early 2000s. Due to thermodynamic noise in
the cavity, the fractional frequency stability of these lasers are at a few 10-16 at 1 s average time.
Among the various paths taken in the search for improvement, a promising candidate is laser
spectroscopy with rare earth doped ions at cryogenic temperatures. With an optimal choice of the
crystalline matrix and dopant ion, very narrow spectroscopic features can be realized using the socalled ‘Spectral Hole Burning’ technique. These holes are then used as a reference to stabilize the
frequency of lasers. Fundamental limit of such a system is currently unknown but expected to be
below 10-18 at 1 s. This internship will contribute to the Spectral Hole Burning experiment of SYRTE.
Central to the SHB experiment is the ultra-low noise heterodyne detection using two phase-locked
lasers. The phase relation between these two continuous wave lasers is locked on a stable microwave signal using an optical phase locked loop (OPLL). The residual relative phase noise between the
lasers enters directly into the detection noise. For the ultimate performance of our detection
scheme, it is therefore crucial to optimize the OPLL.
Conventional solutions based on analog electronics exist since more than 30 years. They constitute
the standard phase lock schemes already present on our experiment. However, the advent of digital
electronics provides the attractive possibilities of agile frequency control and atomization. We have
therefore collaborated with the startup company Koheron for a digital OPLL based on commercial
FPGA (Red Pitaya). The intern will first test the functionalities of the digital OPLL in order to evaluate
its performance in terms of locking bandwidth and residual noise. The former could be potentially
limited by digitization. Optimization should be carried out for our specific system.

Profil recherché

We are looking for a serious candidate with professionalism. Technically, he/she should be familiar
with standard optics, laser, analog and digital electronics. Prior experience with FPGA programming
is appreciated but not necessary. Given the international context of the subject and the laboratory,
technical English is indispensable.

Niveau de qualification requis

Bac + 4/5 et +
  • Employeur
    Laboratoire SYRTE Observatoire de Paris
  • Secteur d’activité de la structure
    Enseignement - Formation - Recherche
  • Effectif de la structure
    De 51 à 250 salariés
  • Site internet de la structure
  • Type de stage ou contrat
    Stage pour lycéens et étudiants en formation initiale
  • Date prévisionnelle de démarrage
  • Durée du stage ou contrat
    Plus de 4 mois et jusqu'à 6 mois
  • Le stage est-il rémunéré ?
  • Niveau de qualification requis

    Bac + 4/5 et +
  • Lieu du stage
    61 Avenue de l'Observatoire
  • Accès et transports
    RER B Denfert Rochereau