Institut France-Comté Electronique Mécanique Thermique et Optique – Sciences et Technologies (FEMTO-ST)

Activities Time-Frequency:

Workforce: 72with: 29 permanents, 43 non-permanent


The Time-Frequency Department (TF) is developing the time keepers necessary for the most modern high-tech applications: space navigation, telecommunications, radar, etc. It brings together work in the field of resonators and oscillators, sensor applications derived from them, and metrology of frequency sources. The TF is essentially a multidisciplinary department where many technologies and scientific fields are associated (electronics, microwave, acoustics, sciences and shaping of crystalline materials, MEMS, photonics, signal processing, atomic physics, ...). The DTF is composed of 3 teams:
- the Acoustoelectronics and Piezoelectricity (ACEPI) team studies monocrystalline piezoelectric materials from the point of view of fundamental properties but also shaping and machining them for time frequency applications. The main objective is to design, realize and characterize bulk acoustic wave resonators and oscillator electronics for ultra-stable time bases and / or sensor applications.
- the team Components and Micro-Acoustic Systems (CoSyMA) concern two classes of applications: on one side, the frequency sources and filters, on the other, the sensors. Within the two application sectors mentioned above, the team's research pursues three objectives of different natures: The improvement of RF passive components exploiting the properties of elastic waves. The development of electronic systems incorporating such components for the intended applications. Multi-scale multiphysics mathematical modeling to improve the understanding and control of the behavior of components or networks of passive components.
- the Waves, Clocks, Metrology and Systems (OHMS) team is involved in the realization of secondary frequency standards and in the phase metrological characterization of oscillators and frequency fluctuations. It is also a partner of the FIRST-TF network and Equipex REFIMEVE + and carries the Equipex OSCILLATOR-IMP.
The three major themes developed within the team are:
> Microwave frequency references: - Cryogenic Saphire Oscillators - Atomic clock and compact clock
> Optical frequency references: - Stabilized lasers and low noise microwave signal generation. Trapped ion optical clock. Connection to the REFIMEVE + network
> Metrology and TF instrumentation: - Digital electronics. Improvement and monitoring of calibration potential of LNE LTFB

Expertise :

  • Oscillators
    • RF and microwave oscillators and synthesis
      • Piezoelectric technologies• Ultra-stable quartz oscillators. Alternative materials to quartz.
        Material shaping for RF acoustic resonators.
        Characterizations: identification of resonator constants, noise behavior, sensitivity to pressure, acceleration and radiation, temperat
      • MEMS technologies• Collective Fabrication of ultra-stable BAW resonators
      • Microwave technologies• Oscillator design for ground and/or on-board applicationscryogenic sapphire oscillators ADEV <1e-15
    • Optical oscillators, lasers
      • Lasers locked to a Fabry-Pérot cavity• Conception, realization and characterization lasers frequency stabilized on Fabry-Perot (ultra-stable) cavities.
      • WGM, gallery modes• WGM resonatorsKerr comb microwave oscillators
      • Frequency combs• 2 frequency combs : Stabilization of optical frequency comb for metrological characterization of optical oscillators and for low noise microwave generation.
      • Laser sources• Characterization of laser sources frequency and intensity noise.
  • Atomic references
    • Micro-wave clocks and subsystems
      • Coherent population trapping (CPT) clocks• Chip scale atomic clock
        High performances CPT clock.
      • Masers• 3 Hydrogen Masers
    • Optical clocks and subsystems
      • Optical ion clocks• Compact Yb+ optical trapped ion clock on a chip
  • Synchronisation, frequency transfer and time scales
    • Micro-wave links
      • GNSS• Software decoding of GPS signals collected from the modulated carrier to the navigation messages.
      • Two way systems• TWSTFT microwave station
    • Fibred optical links
      • Data transfer on a fibre network• White Rabbit
      • Purely optical methods• Transfer of RF and optical reference signals through telecom fibers. uncompensated fiber-links for RF signals with maser-like performances, compensated fiber-links for ultra-pure signals (optical cavities, cryogenic sapphire oscillators)
    • Time scales• UTC(OP)B {Access to UTC(OP)}
  • Specific methods of time-frequency metrology
    • Noise
      • Phase noise, PLL• Mixer-free digital phase noise characterization setup.
        Inherent phase noise measurement system of acoustic resonators (BAW,SAW, HBAR...) 50 kHz-5GHz
        COFRAC labelization for phase noise measurementA few high performance commercial and prototypes instruments for phase noise measurements.
      • Intensity noise• Theoretical models
        Data interpretation
        Prototypes for the moise measurement exhibiting ultimate sensitivity
      • Short term stability, long term stability• Acoustic resonators and RF oscillators aging
        Stability measurements to characterize frequency references, devices, environmental perturbations (temperature, vibrations) …
        COFRAC labelization for Allan deviation measurement
    • High resolution spetroscopy
      • Atomic spectroscopy• Fluorescence spectroscopy.
        Absorption spectroscopy in a discharge lamp
    • Chronometry• A few high-performance commercial instruments for the measurement of time interval (ps resolution)
  • Techniques for time-frequency metrology and applications
    • Electronics
      • Analog electronics• Development of electronic loop filter for the realization of lock.
        Low noise amplifier
        Theoretical background and practical experience in the design of low-noise electronics DC/audio-frequency/RF/microwaves
      • Digital electronics• Microcontroller and embedded linux development, data acquisition and digital control (0-500 MHz), buildroot framework.
        A few digital platforms (Red Pitaya, Zynq etc.)
        Noise in digital systems and FPGAs
      • Acquisition, interfaces, converters• Noise in ADCs, DACs, and DDSs.
    • Mechanics, Ultra-high vacuum, Cryogenics• Standard UHV techniques. turbo-molecular pumping, ion and getter pumps, best pressures below 10-10mbars.
      Pulse-tube cryo-coolers, temperature regulation around 5-6 K and 17 K, vibration isolation.
      Dilution cryogenerator 10 mK.
    • Optics
      • Guided optics, specific optical fibres• Second-harmonic generation in PPLN waveguides. residual phase noise.
      • High sensitivity, low noise photodetectors• Low-noise fluorescence detection setup. photo-multiplier tube, low noise CCD camera.
    • Cooling or trapping techniques
      • Trapped ions• Surface-electrode ion trap, laser Doppler cooling
    • Sensors
      • Piezoelectric, MEMS inertial sensors
      • Pressure sensors

Connected Sectors:

  • Positioning and navigation
    • Radar• High spectral purity oscillators
      Methods and equipment for the measurement of high-purity oscillators
  • Environment and health
    • Atmosphere physics• Ionospheric delay measurement using Very Low Frequency radiofrequency signal propagation.

FIRST-TF Network