131 research outputs found
A simple laser system for atom interferometry
We present here a simple laser system for a laser cooled atom interferometer,
where all functions (laser cooling, interferometry and detection) are realized
using only two extended cavity laser diodes, amplified by a common tapered
amplifier. One laser is locked by frequency modulation transfer spectroscopy,
the other being phase locked with an offset frequency determined by an
Field-Programmable Gate Array (FPGA) controlled Direct Digital Synthesizer
(DDS), which allows for efficient and versatile tuning of the laser frequency.
Raman lasers are obtained with a double pass acousto-optic modulator. We
demonstrate a gravimeter using this laser system, with performances close to
the state of the art
Dick effect in a pulsed atomic clock using Coherent Population Trapping
The Dick effect can be a limitation of the achievable frequency stability of
a passive atomic frequency standard when the ancillary frequency source is only
periodically sampled. Here we analyze the Dick effect for a pulsed vapor cell
clock using coherent population trapping (CPT). Due to its specific
interrogation process without atomic preparation nor detection outside of the
Ramsey pulses, it exhibits an original shape of the sensitivity function to
phase noise of the oscillator. Numerical calculations using a three-level atom
model are successfully compared with measurements; an approximate formula of
the sensitivity function is given as an easy-to-use tool. A comparison of our
CPT clock sensitivity to phase noise with a clock of the same duty cycle using
a two-level system reveals a higher sensitivity in the CPT case. The influence
of a free-evolution time variation and of a detection duration lengthening on
this sensitivity is studied. Finally this study permitted to choose an adapted
quartz oscillator and allowed an improvement of the clock fractional frequency
stability at the level of 3.2x10-13 at 1
Hybridizing matter-wave and classical accelerometers
We demonstrate a hybrid accelerometer that benefits from the advantages of
both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and
long term stability. First, the use of a real time correction of the atom
interferometer phase by the signal from the classical accelerometer enables to
run it at best performances without any isolation platform. Second, a
servo-lock of the DC component of the conventional sensor output signal by the
atomic one realizes a hybrid sensor. This method paves the way for applications
in geophysics and in inertial navigation as it overcomes the main limitation of
atomic accelerometers, namely the dead times between consecutive measurements
Phase noise characterization of sub-hertz linewidth lasers via digital cross correlation
Phase noise or frequency noise is a key metrics to evaluate the short term
stability of a laser. This property is of a great interest for the applications
but delicate to characterize, especially for narrow line-width lasers. In this
letter, we demonstrate a digital cross correlation scheme to characterize the
absolute phase noise of sub-hertz line-width lasers. Three 1,542 nm
ultra-stable lasers are used in this approach. For each measurement two lasers
act as references to characterize a third one. Phase noise power spectral
density from 0.5 Hz to 0.8 MHz Fourier frequencies can be derived for each
laser by a mere change in the configuration of the lasers. This is the first
time showing the phase noise of sub-hertz line-width lasers with no reference
limitation. We also present an analysis of the laser phase noise performance.Comment: 4 pages, 5 figure
High Resolution Frequency Standard Dissemination via Optical Fibre Metropolitan Network
We present in this paper results on a new dissemination system of
ultra-stable reference signal at 100 MHz on a standard fibre network. The 100
MHz signal is simply transferred by amplitude modulation of an optical carrier.
Two different approaches for compensating the noise introduced by the link have
been implemented. The limits of the two systems are analyzed and several
solution suggested in order to improve the frequency stability and to further
extend the distribution distance. Nevertheless, our system is a good tool for
the best cold atom fountains comparison between laboratories, up to 100 km,
with a relative frequency resolution of 10-14 at one second integration time
and 10-17 for one day of measurement. The distribution system may be upgraded
to fulfill the stringent distribution requirements for the future optical
clocks
Long-distance frequency dissemination with a resolution of 10-17
We use a new technique to disseminate microwave reference signals along
ordinary optical fiber. The fractional frequency resolution of a link of 86 km
in length is 10-17 for a one day integration time, a resolution higher than the
stability of the best microwave or optical clocks. We use the link to compare
the microwave reference and a CO2/OsO4 frequency standard that stabilizes a
femtosecond laser frequency comb. This demonstrates a resolution of 3.10-14 at
1 s. An upper value of the instability introduced by the femtosecond
laser-based synthesizer is estimated as 1.10-14 at 1 s
Accurate Bootstrapping of an optical frequency comb to a 1542 nm carrier
International audienc
Remote Generation of an Acurate RF Signal with an Optical Frequency Comb
International audienc
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