P. Lemonde

UPMC, Pittsburgh, Pennsylvania, United States

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Publications (135)181.93 Total impact

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    ABSTRACT: Progress in realizing the SI second had multiple technological impacts and enabled further constraint of theoretical models in fundamental physics. Caesium microwave fountains, realizing best the second according to its current definition with a relative uncertainty of 2–4 × 10−16, have already been overtaken by atomic clocks referenced to an optical transition, which are both more stable and more accurate. Here we present an important step in the direction of a possible new definition of the second. Our system of five clocks connects with an unprecedented consistency the optical and the microwave worlds. For the first time, two state-of-the-art strontium optical lattice clocks are proven to agree within their accuracy budget, with a total uncertainty of 1.5 × 10−16. Their comparison with three independent caesium fountains shows a degree of accuracy now only limited by the best realizations of the microwave-defined second, at the level of 3.1 × 10−16.
    Nature Communications 07/2013; 4. · 10.74 Impact Factor
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    ABSTRACT: In this paper, we review several characteristics of optical lattice clocks as candidates for a future redefinition of the International System of Units (SI) second using an atomic transition in the optical domain, focusing on experiments performed at SYRTE using one mercury (Hg) and two strontium (Sr) optical lattice clocks. Beyond the technical aspects such as the stability and systematic frequency-shift assessments of the clocks, practical aspects have to be considered, such as the careful determination of the optical frequency with respect to the cesium primary standard and the worldwide reproducibility of the clock frequency by local and remote clock comparisons.
    IEEE Transactions on Instrumentation and Measurement 01/2013; 62(6):1568-1573. · 1.71 Impact Factor
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    ABSTRACT: We report the main features and performances of a prototype of an ultra-stable cavity designed and realized by industry for space applications with the aim of space missions. The cavity is a 100 mm long cylinder rigidly held at its midplane by a engineered mechanical interface providing an efficient decoupling from thermal and vibration perturbations. Intensive finite element modeling was performed in order to optimize thermal and vibration sensitivities while getting a high fundamental resonance frequency. The system was designed to be transportable, acceleration tolerant (up to several g) and temperature range compliant [-33°C ; 73°C]. Thermal isolation is ensured by gold coated Aluminum shields inside a stainless steel enclosure for vacuum. The axial vibration sensitivity was evaluated at (4 ± 0.5) × 10<sup>-11</sup>/(m.s<sup>-2</sup>), while the transverse one is < 1 × 10<sup>-11</sup>/(m.s<sup>-2</sup>). The fractional frequency instability is ≲ 1×10<sup>-15</sup> from 0.1 to a few seconds and reaches 5-6×10<sup>-16</sup> at 1s.
    Optics Express 11/2012; 20(23):25409-20. · 3.55 Impact Factor
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    ABSTRACT: We report on the observation of a dc Stark frequency shift at the 10-(13) level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed under vacuum close to the atomic sample. We show that these charges can be eliminated by shining UV light on the dielectric surfaces, and characterize the residual dc Stark frequency shift on the clock transition at the 10-(18) level by applying an external electric field. This study shows that the dc Stark shift can play an important role in the accuracy budget of lattice clocks, and should be duly taken into account.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 03/2012; 59(3):411-5. · 1.80 Impact Factor
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    ABSTRACT: form only given. We will report on the development of optical lattice clocks at LNE-SYRTE. Two strontium and a mercury optical lattice clocks were developed over more than a decade. We will give and overview of this work, emphasizing several unique features of the clocks. We will also describe application of these clocks to fundamental physics tests and as well as work relevant to a possible redefinition of the SI second based on an optical transition.
    Precision Electromagnetic Measurements (CPEM), 2012 Conference on; 01/2012
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    ABSTRACT: Two optical lattice clocks operated on the transition 1S0-3P0 of the 87Sr atom are now operational at the LNE-SYRTE laboratory, their comparison aims at demonstrating that no systematic effect has been overlooked in their respective accuracy budgets. In this proceeding we focus only on trapping effects, we discuss technical aspects of the calibration of the lattice induced light shifts, and we show the observation of the second order light shift. Data resulting from the comparisons are reported and discussed.
    European Frequency and Time Forum (EFTF), 2012; 01/2012
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    ABSTRACT: We report the main characteristics and performances of the first - to our knowledge - prototype of an ultra-stable cavity designed and produced by industry with the aim of space missions. Finite element modeling was performed in order to minimize thermal and vibration sensitivities. The system was designed to be transportable, acceleration tolerant (up to several g) and temperature range compatible (ΔT ~ 40 K). The optical axis of the 100 mm long cavity is vertical. The spacer is made from Ultra-Low Expansion (ULE) glass and mirrors substrate from fused silica to reduce the thermal noise limit to 4×10-16. The axial vibration sensitivity was evaluated at (4 ± 0.5) ×10-11 /(ms-2), while the transverse one is
    European Frequency and Time Forum (EFTF), 2012; 01/2012
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    ABSTRACT: Two optical lattice clocks operated on the transition 1S0-3P0 of the 87Sr atom are now operational at the LNE-SYRTE laboratory, their comparison aims at demonstrating that no systematic effect has been overlooked in their respective accuracy budgets. In this proceeding we focus only on trapping effects, we discuss technical aspects of the calibration of the lattice induced light shifts, and we show the observation of the second order light shift. Data resulting from the comparisons are reported and discussed.
    Frequency Control Symposium (FCS), 2012 IEEE International; 01/2012
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    ABSTRACT: Atomic Clock Ensemble in Space (ACES) is an ESA mission in fundamental physics based on a new generation of clocks operated in the microgravity environment of the International Space Station. Installed at the external payload facility of the Columbus module, ACES will accommodate two atomic clocks: PHARAO, a primary frequency standard based on samples of laser cooled Cs atoms, and the active H-maser SHM. The two on-board clocks will generate a time scale with fractional frequency instability and inaccuracy of a few parts in 1016. The ACES frequency reference will be distributed to ground by a MicroWave Link (MWL) and used to compare distant clocks. These comparisons will allow precision tests of the Einstein's theory of general relativity, including a measurement of the gravitational red-shift, a search for time variations of fundamental constants, and tests of the standard model extension. ACES will also support applications in different areas of research, including geodesy and GNSS remote sensing. A link in the optical domain is also part of ACES for time transfer experiments, ranging, and analysis of atmospheric propagation delays. The engineering models of the ACES clocks and main subsystems have been successfully tested, and manufacturing of the flight models has been started. Mission concept, scientific objectives, and status of ACES will be presented together with the latest test results.
    Acta Astronautica. 12/2011; 69(2011-07-31-11-12):929-938.
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    ABSTRACT: Mechanical vibration induced frequency noise is dominated at low Fourier frequencies in a fiber spool stabilized laser. Environmental vibration causes mechanical deformations in the fiber which induce phase fluctuations and then convert into excess frequency noise to the lasers. Therefore, the spool which supports the fiber plays a critical role in this frequency noise conversion. We have studied several different structures of spool. The preliminary results are about 3×10<sup>-10</sup>/m s<sup>-2</sup> for accelerations along the spool axis. In this paper, we describe the development of a spool design which is optimized for low vibration sensitivity along all spatial directions. Both simulations by Finite Element Modeling (FEM) and vibration sensitivity measurements are presented.
    Frequency Control and the European Frequency and Time Forum (FCS), 2011 Joint Conference of the IEEE International; 06/2011
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    ABSTRACT: We present a comprehensive study of the frequency shifts associated with the lattice potential in a Sr lattice clock by comparing two such clocks with a frequency stability reaching 5×10(-17) after a 1 h integration time. We put the first experimental upper bound on the multipolar M1 and E2 interactions, significantly smaller than the recently predicted theoretical upper limit, and give a 30-fold improved upper limit on the effect of hyperpolarizability. Finally, we report on the first observation of the vector and tensor shifts in a Sr lattice clock. Combining these measurements, we show that all known lattice related perturbations will not affect the clock accuracy down to the 10(-17) level, even for lattices as deep as 150 recoil energies.
    Physical Review Letters 05/2011; 106(21):210801. · 7.73 Impact Factor
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    ABSTRACT: In this review, we discuss the impact of the development of lasers on ultracold atoms and molecules and their applications. After a brief historical review of laser cooling and Bose-Einstein condensation, we present important applications of ultra cold atoms, including time and frequency metrology, atom interferometry and inertial sensors, atom lasers, simulation of condensed matter systems, production and study of strongly correlated systems, and production of ultracold molecules.
    Comptes Rendus Physique 05/2011; 12:417-432. · 1.82 Impact Factor
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    ABSTRACT: We present a comprehensive study of the frequency shifts associated with the lattice potential in Sr lattice clocks. By comparing two such clocks with a frequency stability better than 5.10 17 after one hour of averaging time, and varying the lattice depth up to U0 = 900 Er with Er being the recoil energy, we evaluate lattice related shifts with an unprecedented accuracy. Three different types of frequency shifts induced by the lattice have been identified as potential limitations to the accuracy of optical lattice clocks (1). The first one is related to the non scalar feature of the atom-lattice interaction, which results from the atomic hyperfine structure (1,2). It induces a small vector and tensor component in the confinement potential. In addition to the intensity dependence, this makes the light shift slightly dependent on the lattice polarization and geometry. We report the first observation of these effects in a Sr lattice clock and measure them with percent accuracy. We also show that the tensor effect can be used to operate a clock with 87 Sr in an optimal 3D lattice.
    01/2011;
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    ABSTRACT: In this paper, we review several aspects of the frequency stability of optical lattice clocks. We describe a new ultra-stable cavity design with reduced thermal noise and record frequency stability (below 10−15), as well as a non-destructive detection scheme for measuring the clock transition probability. Given the experimental parameters we measured, we simulate different sequence strategies for optimizing the stability. Finally, we report on the development of a second optical lattice clock and simulate several comparison strategies. In particular, we show by a numerical method that a stability as low as 2×10−16τ−1/2 can be reached with optical lattice clocks, and we show how to demonstrate this stability with a double clock system.
    New Journal of Physics 06/2010; 12(6):065026. · 4.06 Impact Factor
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    ABSTRACT: Very low frequency noise laser sources are key elements of many applications, such as: atom or ion optical clocks, ultra stable microwave (MW) frequency generation, gravitational wave detection , ultra stable optical frequency transfer, and so on.The laser frequency locking technique developed by Pound, Drever and Hall (PDH) is widespread as the commonly used method of laser frequency stabilization on optical cavities, and it has been successfully demonstrated on lasers of various wavelengths. It led to a fractional frequency instability lower than 10 -15 for 1 s averaging times and subhertz line width. This approach has intrinsically two weaknesses. First, it requires fine alignment of free space optical components, tight polarization adjustment, and spatial mode matching. In addition, the cavity has to be housed in a high vacuum enclosure with thermal radiation shielding. This makes the system relatively expensive, bulky and fragile. The second weakness is that the PDH method does not allow tuning the laser frequency. An alternative method is to use a two arm (Michelson or Mach-Zehnder) interferometer to measure the frequency fluctuations during a fixed time delay. This method requires a relatively large arm imbalance to obtain sufficient frequency discriminator sensitivity. Indeed, with a Michelson interferometer, the quality factor is proportional to the fiber delay. For example, using a 5 km fiber delay line the quality factor of the interferometer is about 30 billions for a 1.55 μm wavelength laser, which is equivalent to the quality factor of a 10 c m Fabry Perot cavity with finesse about 230 thousands. This stabilization technique allows a more robust, simpler, cheaper, transportable and frequency tunable laser with low frequency noise. In the experiment, the author use the frequency shifted heterodyne Michelson interferometer to stabilize laser frequency. Since the laser frequency can be chirped by setting a frequency offset onto the dem- dulation signal, the laser was called an “agile laser”.
    EFTF-2010 24th European Frequency and Time Forum; 06/2010
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    ABSTRACT: We describe the realization of a 5 km free-space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long-distance frequency transfer.
    Optics Letters 05/2010; 35(9):1479-81. · 3.39 Impact Factor
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    ABSTRACT: We discuss the minimization of the Dick effect in an optical lattice clock. We show that optimizing the time sequence of operation of the clock can lead to a significant reduction of the clock stability degradation by the frequency noise of the interrogation laser. By using a nondestructive detection of the atoms, we are able to recycle most of the atoms between cycles and consequently to strongly reduce the time spent capturing the atoms in each cycle. With optimized parameters, we expect a fractional Allan deviation better than 2 x 10(-16tau-1/2) for the lattice clock.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 03/2010; 57(3):623-8. · 1.80 Impact Factor
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    Optics Express 02/2010; 18(4):3284-3297. · 3.55 Impact Factor
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    ABSTRACT: We report on a fiber-stabilized agile laser with ultra-low frequency noise. The frequency noise power spectral density is comparable to that of an ultra-stable cavity stabilized laser at Fourier frequencies higher than 30 Hz. When it is chirped at a constant rate of approximately 40 MHz/s, the max non-linearity frequency error is about 50 Hz peak-to-peak over more than 600 MHz tuning range. The Rayleigh backscattering is found to be a significant frequency noise source dependent on fiber length, chirping rate and the power imbalance of the interferometer arms. We analyze this effect both theoretically and experimentally and put forward techniques to reduce this noise contribution.
    Optics Express 02/2010; 18(4):3284-97. · 3.55 Impact Factor
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    ABSTRACT: We present work in progress at SYRTE, APC and ARTEMIS aiming at stabilizing the frequency of a Nd:YAG laser using saturated absorption spectroscopy of molecular iodine 127I2. The novel design of the LASIC project allows for robustness and compacity while achieving high-performance phase noise suppression. The project is a follow-up of the laser stabilization work started at Artemis and continued at APC. The use of a low-finesse bow-tie optical cavity around the iodine absorber, combined with an adapted high-frequency modulation of the laser phase -NICE-OHMS technique-yields shot-noise limited saturated absorption signals with cavity-enhanced signal-to-noise ratios. Residual fractional frequency instability in terms of Allan Std. Deviation is expected below 10-14 @1s integration time and down to 10-15 over several hours. The compact iodine / cavity design, and performance well above LISA requirements make this project an interesting candidate for the space-based Gravitational Waves detector. We discuss the scientific background and outline of this project within the LISA framework, as well as its potential impact on other stringent technical requirements of the LISA project (e.g. U.S.O. clock-stability, arm-length measurements. . . ). We also present other possible applications for space projects involving interferometry, laser ranging or onboard ultrastable oscillators.
    01/2010;

Publication Stats

2k Citations
181.93 Total Impact Points

Institutions

  • 2009–2013
    • UPMC
      Pittsburgh, Pennsylvania, United States
  • 2003–2012
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • Laboratoire National de Métrologie et d'Essais
      Lutetia Parisorum, Île-de-France, France
  • 1999–2010
    • Observatoire de Paris
      Lutetia Parisorum, Île-de-France, France
  • 2008–2009
    • Université Paris 13 Nord
      • LPL Laboratoire de physique des lasers
      Villetaneuse, Ile-de-France, France
  • 2007
    • Ecole Normale Supérieure de Paris
      • Laboratoire Kastler-Brossel
      Paris, Ile-de-France, France