J. Guéna

Ultralow noise microwave generation with fiber-based optical frequency comb and application to atomic fountain clock

We demonstrate the use of a fiber-based femtosecond laser locked onto an ultrastable optical cavity to generate a low-noise microwave reference signal. Comparison with both a cryogenic sapphire oscillator (CSO) and a titanium-sapphire-based optical frequency comb system exhibit a stability of about 3×10−15 between 1 and 10 s. The microwave signal from the fiber system is used to perform Ramsey spectroscopy in a state-of-the-art cesium fountain clock. The resulting clock is compared to the CSO and exhibits a stability of 3.5×10−14τ−1/2.

Experimental realization of an optical second with strontium lattice clocks

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).

Neutral atom frequency reference in the deep ultraviolet with fractional uncertainty = 5.7×10(-15).

We present an assessment of the (6s) 1S0 ↔ (6s7s) 3P0 clock transition frequency in Hg with an uncertainty reduction of nearly three orders of magnitude and demonstrate an atomic quality factor, Q, of ∼10. The Hg atoms are confined in a vertical lattice trap with light at the newly determined magic wavelength of 362.5697±0.0011 nm and at a lattice depth of 20ER. The atoms are loaded from a single stage magneto-optical trap with cooling light at 253.7 nm. The high Q factor is obtained with an 80ms Rabi pulse at 265.6 nm. The frequency of the clock transition is found to be 1 128 575 290 808 162.0 ± 6.4 (sys.) ± 0.3 (stat.) Hz (fractional uncertainty = 5.7×10). Neither an atom number nor second order Zeeman dependence have yet to be detected. Only three laser wavelengths are used for the cooling, lattice trapping, probing and detection.

Comparing a mercury optical lattice clock with microwave and optical frequency standards

In this paper we report the evaluation of an optical lattice clock based on neutral mercury with a relative uncertainty of

UTC(OP) based on LNE-SYRTE atomic fountain primary frequency standards

1.7\times {10}^{-16}

New measurement of the rubidium hyperfine frequency using LNE-SYRTE fountain ensemble

. Comparing this characterized frequency standard to a 133Cs atomic fountain we determine the absolute frequency of the

Flywheel oscillator for atomic fountain clocks using ultra-stable lasers and a fiber-based optical frequency comb

{}^{1}{{\rm{S}}}_{0}\to {}^{3}{{\rm{P}}}_{0}

Comparisons between 3 fountain clocks at LNE-SYRTE

transition of 199Hg as

Performances of UTC(OP) based on LNE-SYRTE atomic fountains

{\nu }_{\mathrm{Hg}}=1128\,575\,290\,808\,154.62\,\mathrm{Hz}\pm 0.19\,\mathrm{Hz}(\mathrm{statistical})\pm 0.38\,\mathrm{Hz}

Design Details of FOCS-2, an Improved Continuous Cesium Fountain Frequency Standard

(systematic), limited solely by the realization of the SI second. Furthermore, by comparing the mercury optical lattice clock to a 87Rb atomic fountain, we determine for the first time to our knowledge the ratio between the 199Hg clock transition and the 87Rb ground state hyperfine transition. Finally we present a direct optical to optical measurement of the 199Hg/87Sr frequency ratio. The obtained value of