Systèmes de Référence Temps-Espace (SYRTE) Category: Research or metrology institute

Activities Time-Frequency:

Workforce: 90with: 40 permanents, 50 non-permanent

PARIS, France

The SYRTE, more specifically its division known as the LNE-SYRTE, has a mandate from the National Laboratory of Metrology and Testing (LNE) for realizing the national references for time and frequency, ensuring their traceability at the international level and making them available to users. It develops ambitious research programs in the field of time and frequency, especially concerning microwave and optical frequency standards, time scales and comparisons between frequency and time standards operating in different spectral domains and/or at long distances (continental or intercontinental) from each other. In this work it uses and develops many experimental techniques, such as precision mechanical engineering, RF and microwave electronics, optics, laser cooling and manipulation of atoms, spectroscopy, oscillator and laser stabilisation, optical frequency combs, etc. It realizes and makes available the unit of time, the second, the national time scale UTC(OP) and legal time, and French atomic time TA(F) in partnership with a network of French laboratories. It collaborates with the International Bureau of Weights and Measures (BIPM) to contribute to the international reference time UTC and to ensure the traceability of UTC(OP). It also carries out advanced research in the field of inertial sensors based on atomic interferometry, and is charged by the LNE with a mission in gravimetry. It applies these capabilities in other areas of research such as fundamental physics, geodesy, gravitational waves, etc. It participates in major projects and networks in all areas of its work. It has many industrial collaborations and attaches a particular importance to technology transfer to industry. Other divisions of SYRTE work in related fields such as VLBI, celestial reference systems, Earth rotation, and the history of astronomy and science.

Expertise :

  • Oscillators
    • RF and microwave oscillators and synthesis
      • Microwave technologies• Low phase noise oscillators and frequency chainsmicrowave synthesis from optical sources
      • Disciplined oscillators• Digital and analog PLL with a large spectrum of performance and caracteristic timescales (from a few 100 nanoseconds to several days for feed-back time constant)
    • Optical oscillators, lasers
      • Lasers locked to a Fabry-Pérot cavity• Realization and utilization of multiple systems (>10) operating at various wavelengths from the visible to the near IR.
        Cavity length from 10cm to 40cm
      • Lasers locked to a fibre delay line• Past R&D activity. Utilization of existing systems in experiments
      • Lasers locked with Spectral Hole Burning effect (SHB)• On going R&D project. Servo loop using digital technique Development of ultra-low vibration closed-cycle cryostat.
      • Lasers locked to an atomic or molecular line• Several optical frequency standards of extremely high absolute accuracy (2 Strontium Sr, 1 Mercury Hg)
        Compact and high performance optical frequency standard based on molecular transition in iodine I2
      • Frequency combs• Multiple fully functional systems (1 Ti:Sapphire Titane Sapphire, 5 Erbium Er-doped fiber systems)
        Operationnal activity with continuous measurement for months
        Transfer of spectral purity between wavelengths
        Ultra-low phase noise microwave signal gen
      • Laser sources• Developments of extended cavity diode lasers technologies
        Frequency locking of lasers on external cavities or atomic/molecular lines
        Amplitude stabilization of laser sources
  • Atomic references
    • Micro-wave clocks and subsystems
      • Cold atoms• Atomic fountain clocks
        Cold atom space clock (ACES/PHARAO)
        Isotropic light cooling clock
        Cesium Cs, Rubidium Rb
      • Thermal beam clocks• Past R&D and continuous operation during several years
      • Optical pumping cell clocks• Past R&D activity, industrial transfer
      • Coherent population trapping (CPT) clocks• Continuous interrogation
        Pulsed interrogation (Ramsey)
        Laser frequency generation by direct modulation, electro-optical modulator (EOM), phase locking (PLL)
        Polarisation modulation
      • Masers• Utilization for timescales
    • Optical clocks and subsystems
      • Optical neutral atomic clocks• 3 ultra-high performance (accurracy and stability) systems: 2 Strontium Sr, 1 Mercury Hg
        Use of non destructive measurements for improving short term stability
  • Synchronisation, frequency transfer and time scales
    • Micro-wave links
      • GNSS• GPS, GLONASS, Galileo, EGNOS
        Galileo System Time, EGNOS Network Time
        Single and dual frequency
        Code and phase methods: P3, PPP, etc
        Relative and absolute receiver calibration
      • Two way systems• Two Way Satellite Time and Frequency Transfer
        Satellite simulator
        Code and phase
        Software-defined radio modem
        Modeling of the ACES micro-wave link (MWL)
      • Radio links• France Inter
      • Wired links• Local high-performance time and frequency distribution
    • Optical links in free space
      • Pulsed optical links in free space• Collaboration with the T2L2 experiment of OCA/Geoazur
      • Continuous optical links in free space• Past R&D activity
    • Fibred optical links
      • Data transfer on a fibre network• Local area and long-distance time and frequency transfer on packet-switched networks
        Dual fibre, uni-directional
        Protocols: NTP, PTP, White Rabbit
      • Purely optical methods• Ultra-stable optical carrier frequency transfer
        Bi-directional dark channel
        Repeater laser station
        RF and time transfer
    • Time scales• Realisation of highly stable and accurate time scales, steered using primary and secondary frequency standards (atomic fountains, optical clocks)
      Realisation of the national reference time scale UTC(OP), the basis for legal time
      Steering remote time scales
      Realisation of French Atomic Time, TA(F)
  • Specific methods of time-frequency metrology
    • Noise
      • Phase noise, PLL• RF and microwave domains
        Optical domain
        Very low phase noise
        Frequency agility
      • Intensity noise• Amplitude servo of continuous and pulsed lasers
      • Short term stability, long term stability• Variances and deviations (Allan, ADEV, MDEV, TDEV)
        Characterisation of oscillator and laser stability
        Characterisation of atomic clock stability
        Characterisation of time and frequency transfer stability
    • Systematics, Accuracy, Calibration
      • Systematics in atom-light interaction• Black body radiation shift
        collisional shiftlight shift
        distributed cavity phase shift
        wavefront aberrations
        Stark and Zeeman effects
      • Systematics in time transfer methods• Ionospheric delay
        chromatic dispersion of optical fibre
        electronic delay calibration
    • High resolution spetroscopy
      • Atomic spectroscopy• Atomic frequency references (Cesium Cs, Rubidium Rb, Strontium Sr, Mercury Hg, Europium 3+ Eu3+)
      • Molecular spectroscopy• Molecular frequency references (Iodine I2)
  • Techniques for time-frequency metrology and applications
    • Electronics
      • Analog electronics• Design, realization and test of low current and voltage noise circuits
        low noise photodiodes from DC to microwave ultra low phase noise RF and microwave circuit servo loops frequency multiplication and division
      • Digital electronics• Utlization of ADC, DAC, FPGA, Micro-controlers and computer control of complex experimental apparatus
      • Acquisition, interfaces, converters• Utlization of ADC, DAC, sampling frequencie from the kHz to the GHz range
    • Mechanics, Ultra-high vacuum, Cryogenics• Design and realization of precision mechanicsdesign and realization of ultra-high vacuum systemsutilization and characterization of low noise 4K cryostats
    • Optics
      • Guided optics, specific optical fibres• Utilization of SMF, PM and PCF fibres at various wavelengths in the visible and near IR domains
        noise cancelling of short (meter) to continental scale fiber links
        highly stable PM and SM beam splitters
        waveguide optical frequency doublers
      • High sensitivity, low noise photodetectors• InGaAs Indium gallium arsenide and Si Silicon
        GaAs Gallium arsenide photoconductors
        pin MUTC photodiode
      • Control of the optical beam characteristics• Beam shape analizis
        measure and servo of beam power
        measure and servo of beam pointing instability
    • Cooling or trapping techniques
      • Cooling, trapping of atoms• Laser cooling methods: optical molasses, 2D and 3D magneto-optical traps (MOT), isotropic light, evaporative cooling (optical, magnetic), optical lattices, dipolar traps, cooling and trapping on chip
        Ultra-cold atoms
        On-demand realization of cold atomic sources (2D optical magnetic traps)
    • Interferometry techniques
      • Atom interferometry techniques• Atomic beam splitter (Raman, Bragg)
        Atoms in free fall
        Trapped and guided atoms
    • Sensors
      • Atomic inertial sensors• Cold atom absolute gravimeters, gradiometers and gyrometers
        Cold atoms in free fall, optical lattices, trapped and guided on atom chips
        Accelerometer of the giant interferometer MIGA

Connected Sectors:

  • Fundamental science
    • Fundamental metrology• Definition and realisation of the SI second
      Calibration of TAI
      Contribution to UTC
      French legal time
      Gravimeter for the Watt balance
    • Tests of fundamental physics• Test of the equivalence principle, Lorentz invariance
      Search for variations of the fundamental constants
      Search for effects of dark matter on atomic clocks
      Study of the Casimir-Polder effect
      Tests of forces at short distances
    • Astronomy, astrophysics (radioastronomy, VLBI, gravitational waves sensors)• MIGA
      earth rotation
      celestial reference frames
      expertise and support for timescales and synchronisation for astronomy
  • Positioning and navigation
    • Satellite positioning, GNSS• Contributions to the EGNOS and Galileo time scales, notably to the link to UTC
    • Inertial navigation• Development of new atomic clock and sensor technologies and transfer to industry
    • Radar• Development of low noise microwave sources
  • Network synchronisation
    • Telecommunications• Expertise and support for the provision of time and frequency references (syntonisation and synchronisation) to industry and other users.
      Synchronisation of telecom operators
    • Cyber security• Expertise and support for the provision of time and frequency references (syntonisation and synchronisation) to industry and other users.
    • Smart grids• Expertise and support for the provision of time and frequency references (syntonisation and synchronisation) to industry and other users.
    • Bank transactions• Expertise and support for the provision of time and frequency references (syntonisation and synchronisation) to industry and other users.
    • Transportation networks
  • Environment and health
    • Geoscience (geodesy, geophysics)• Chronometric levelling
      High-sensitivity absolute atomic gravimeter
  • Arts, Languages, human and social sciences
    • Concepts of precision and accuracy• Definition and metrological characterisation of uncertainty
    • History of science, philosophy• Historical instruments
      Development of the concept of measurement precision (17th-18th centuries)
    • Arts• Support for sundial design

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