90 research outputs found
Atomic fountains and optical clocks at SYRTE: status and perspectives
In this article, we report on the work done with the LNE-SYRTE atomic clock
ensemble during the last 10 years. We cover progress made in atomic fountains
and in their application to timekeeping. We also cover the development of
optical lattice clocks based on strontium and on mercury. We report on tests of
fundamental physical laws made with these highly accurate atomic clocks. We
also report on work relevant to a future possible redefinition of the SI
second
An Optical Lattice Clock with Spin-polarized 87Sr Atoms
We present a new evaluation of an 87Sr optical lattice clock using spin
polarized atoms. The frequency of the 1S0-3P0 clock transition is found to be
429 228 004 229 873.6 Hz with a fractional accuracy of 2.6 10^{-15}, a value
that is comparable to the frequency difference between the various primary
standards throughout the world. This measurement is in excellent agreement with
a previous one of similar accuracy
Near-to mid-IR spectral purity transfer with a tunable frequency comb: methanol frequency metrology over a record frequency span
We report the development and operation of a frequency-comb-assisted
high-resolution mid-infrared molecular spectrometer combining high spectral
purity, SI-traceability, wide tunability and high sensitivity. An optical
frequency comb is used to transfer the spectral purity of a SI-traceable 1.54
m metrology-grade frequency reference to a 10.3 m quantum cascade
laser (QCL). The near-infrared reference is operated at the French
time/frequency metrology institute, calibrated there to primary frequency
standards, and transferred to Laboratoire de Physique des Lasers via the
REFIMEVE fiber network. The QCL exhibits a sub-10 --15 frequency stability from
0.1 to 10 s and its frequency is traceable to the SI with a total uncertainty
better than 4 x 10 --14 after 1-s averaging time. We have developed the
instrumentation allowing comb modes to be continuously tuned over 9 GHz
resulting in a QCL of record spectral purity uninterruptedly tunable at the
precision of the reference over an unprecedented span of 1.4 GHz. We have used
our apparatus to conduct sub-Doppler spectroscopy of methanol in a multi-pass
cell, demonstrating state-of-art frequency uncertainties down to the few
kilohertz level. We have observed weak intensity resonances unreported so far,
resolved subtle doublets never seen before and brought to light discrepancies
with the HITRAN database. This demonstrates the potential of our apparatus for
probing subtle internal molecular processes, building accurate spectroscopic
models of polyatomic molecules of atmospheric or astrophysical interest, and
carrying out precise spectroscopic tests of fundamental physics
Experimenting an optical second with strontium lattice clocks
Progress in realizing the SI second had multiple technological impacts and
enabled to further constraint theoretical models in fundamental physics.
Caesium microwave fountains, realizing best the second according to its current
definition with a relative uncertainty of 2-4x10^(-16), have already been
superseded by atomic clocks referenced to an optical transition, both more
stable and more accurate. Are we ready for a new definition of the second? Here
we present an important step in this direction: 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 1.6x10^(-16). Their comparison with three independent caesium
fountains shows a degree of reproducibility henceforth solely limited at the
level of 3.1x10^(-16) by the best realizations of the microwave-defined second.Comment: 9 pages, 4 figures, 2 table
Development of a strontium optical lattice clock for the SOC mission on the ISS
Ultra-precise optical clocks in space will allow new studies in fundamental
physics and astronomy. Within an European Space Agency (ESA) program, the Space
Optical Clocks (SOC) project aims to install and to operate an optical lattice
clock on the International Space Station (ISS) towards the end of this decade.
It would be a natural follow-on to the ACES mission, improving its performance
by at least one order of magnitude. The payload is planned to include an
optical lattice clock, as well as a frequency comb, a microwave link, and an
optical link for comparisons of the ISS clock with ground clocks located in
several countries and continents. Within the EU-FP7-SPACE-2010-1 project no.
263500, during the years 2011-2015 a compact, modular and robust strontium
lattice optical clock demonstrator has been developed. Goal performance is a
fractional frequency instability below 1x10^{-15}, tau^{-1/2} and a fractional
inaccuracy below 5x10^{-17}. Here we describe the current status of the
apparatus' development, including the laser subsystems. Robust preparation of
cold {88}^Sr atoms in a second stage magneto-optical trap (MOT) is achieved.Comment: 27 Pages, 15 figures, Comptes Rendus Physique 201
Development of a strontium optical lattice clock for the SOC mission on the ISS
The ESA mission "Space Optical Clock" project aims at operating an optical
lattice clock on the ISS in approximately 2023. The scientific goals of the
mission are to perform tests of fundamental physics, to enable space-assisted
relativistic geodesy and to intercompare optical clocks on the ground using
microwave and optical links. The performance goal of the space clock is less
than uncertainty and
instability. Within an EU-FP7-funded project, a strontium optical lattice clock
demonstrator has been developed. Goal performances are instability below and fractional inaccuracy .
For the design of the clock, techniques and approaches suitable for later space
application are used, such as modular design, diode lasers, low power
consumption subunits, and compact dimensions. The Sr clock apparatus is fully
operational, and the clock transition in Sr was observed with linewidth
as small as 9 Hz.Comment: 12 pages, 8 figures, SPIE Photonics Europe 201
First-order thermal insensitivity of the frequency of a narrow spectral hole in a crystal
International audienc
First-order thermal insensitivity of the frequency of a narrow spectral hole in a crystal
International audienc
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