Expertise :

• Oscillators
  • RF and microwave oscillators and synthesis
    • Microwave technologies• Microwave pulse excitation of rotational transition in molecules
  • Optical oscillators, lasers
    • Lasers locked to a Fabry-Pérot cavity• Semiconductor laser at 1.5 µm stabilized onto confocal Fabry-Perot cavity for frequency stability transfer.Ar+ argon laser prestabilized onto Fabry-Perot cavity at 514 nm and at 501 nm: linewidth of 30 kHz.Semiconductor laser at 1.5 µm stabilized onto a ring fiber cavity.
    • Lasers locked to an atomic or molecular line• Mid-infrared lasers around 10 µm stabilized on molecular rovibrational lines (SF6 Sulfur hexafluoride or OsO4 Osmium tetroxide), detected with a saturated absorption scheme, possibly in transmission of a Fabry-Perot cavity.Lasers emitting in the near infrared (1.5 µm) locked onto molecular rovibrational line (HCN Hydrogen cyanide or C2H2 Acetylene), detected in linear or saturated absorption.Ar+ argon laser locked onto iodine I2 transitions at 514 nm and 501 nm in cell.
    • Frequency combs• Optical frequency comb around 1.5 µm :comb stabilisation on an optical reference transmitted from Syrte by an optical link, dedicated servo loops, comb tuning on 2.5 GHzstabilisation of a quantum cascade laser on this comb. Semiconductor frequency combs at 1.55 µm: stabilization of the comb by optical injection of a stable CW source.
    • Laser sources• Low noise quantum cascade laser (with home-made power supply) around 10 µmLow-noise home-made carbon dioxide CO2 laser around 9-11 µm
• Synchronisation, frequency transfer and time scales
  • Fibred optical links
    • Purely optical methods• Optical link for ultrastable RF and optical frequency transfer. Active compensation of the propagation phase noise or passive compensation by two-way methodesDevelopment of repeater laser stations, extraction stations and multi-user stations.
• Specific methods of time-frequency metrology
  • Noise
    • Phase noise, PLL• Numerous developments concerning PLLs and servocontrols
    • Intensity noise• Narrow band noise rejection by digital device (70 dB rejection)
    • Short term stability, long term stability• Stabilization of visible and IR laser sources (argon Ar+ laser at 515 nm and 501 nm, CO2 laser and QCL at 10 µm, fiber and semiconductor lasers at 1.5 µm)
      Stabilization of a semiconductor frequency comb at 1.5 µm: stabilization of the comb by optical injection of a stable CW source
      Stabilization of a 1.5 µm fiber optic comb with optical or RF reference, frequency sweep of the stabilized comb
  • Systematics, Accuracy, Calibration
    • Systematics in atom-light interaction• Study of the systematic effects in molecular spectroscopy: in saturated absorption, 2-photon and Ramsey fringes for rovibrational transitions around 10 µm. in saturation spectroscopy and Raman spectroscopy of iodine I2 at 514 nm and 501 nm.
    • Systematics in time transfer methods• Fundamental and technological effects limiting the ultrastable frequency transfer over an optical link
  • High resolution spetroscopy
    • Molecular spectroscopy• Doppler-free spectroscopy of electronic transitions of molecular iodine I2 in cell near the dissociation limit: saturated absorption spectroscopy and Raman spectroscopy, narrow lines.
      Rovibrational Doppler-free spectroscopy at 10 µm of molecules (NH3 Ammonia, SF6 Sulfur hexafluoride, ...) in a cell or a beam: saturated and two-photon absorption, Ramsey fringes, slow molecules detection, record resolution and uncertainty on frequency measurements, free-induction decay detection