314 research outputs found
Absolute frequency measurement of 12C16O2 laser lines with a femtosecond laser comb and new determination of the 12C16O2 molecular constants and frequency grid
Absolute frequency measurements of a CO2 laser stabilized on saturated absorption resonances of CO2 laser lines are reported. They were performed using a femtosecond-laser frequency comb generator and two laser diodes at 852 nm and 782 nm as intermediate oscillators, with their frequency difference phase-locked to the CO2 laser. 20 12C16O2 laser lines in the P and R bands at 9 µm were measured with a relative uncertainty of a few 10-12 limited by the CO2 frequency reproducibility. A new determination of the CO2 molecular constants was obtained from these data and previous measurements in the 10 µm band. The CO2 frequency grid was also calculated, with an improvement of two orders of magnitude compared to the previous grid of Maki et al [A.G. Maki, C.C. Chou, K. Evenson, L.R. Zink and J.T. Shy, J. Mol. Spectrosc. 167, (1994) 211-224]
Two-Way Optical Frequency Comparisons Over 100km Telecommunication Network Fibers
By using two-way frequency transfer, we demonstrate ultra-high resolution
comparison of optical frequencies over a telecommunication fiber link of 100 km
operating simultaneously digital data transfer. We first propose and experiment
a bi-directional scheme using a single fiber. We show that the relative
stability at 1 s integration time is 7 10^18 and scales down to 5 10^21. The
same level of performance is reached when an optical link is implemented with
an active compensation of the fiber noise. We also implement a real-time
two-way frequency comparison over a uni-directional telecommunication network
using a pair of parallel fibers. The relative frequency stability is 10^15 at 1
s integration time and reaches 2 10^17 at 40 000 s. The fractional uncertainty
of the frequency comparisons was evaluated for the best case to 2 10^20. These
results open the way to accurate and high resolution frequency comparison of
optical clocks over intercontinental fiber networks
Probing weak force induced parity violation by high resolution mid-infrared molecular spectroscopy
To date no experiment has reached the level of sensitivity required to
observe weak nuclear force induced parity violation (PV) energy differences in
chiral molecules. In this paper, we present the approach, adopted at
Laboratoire de Physique des Lasers (LPL), to measure frequency differences in
the vibrational spectrum of enantiomers. We review different spectroscopic
methods developed at LPL leading to the highest resolutions, as well as 20
years of CO2 laser stabilization work enabling such precise measurements. After
a first attempt to observe PV vibrational frequency shifts using sub-Doppler
saturated absorption spectroscopy in a cell, we are currently aiming at an
experiment based on Doppler-free two-photon Ramsey interferometry on a
supersonic beam. We report on our latest progress towards observing PV with
chiral organo-metallic complexes containing a heavy rhenium atom
10 um wavefront spatial filtering: first results with chalcogenide fibers
Wavefront cleaning by single-mode fibers has proved to be efficient in
optical-infrared interferometry to improve calibration quality. For instance,
the FLUOR instrument has demonstrated the capability of fluoride glass
single-mode fibers in this respect in the K and L bands. New interferometric
instruments developped for the mid-infrared require the same capability for the
8-12 um range. We have initiated a program to develop single-mode fibers in the
prospect of the VLTI mid-infrared instrument MIDI and of the ESA/DARWIN and
NASA/TPF missions that require excellent wavefront quality. In order to
characterize the performances of chalcogenide fibers we are developping, we
have set up an experiment to measure the far-field pattern radiated at 10 um.
In this paper, we report the first and promising results obtained with this new
component.Comment: Conference "Interferometry for Optical Astronomy II", SPIE 200
Mid-IR frequency measurement using an optical frequency comb and a long-distance remote frequency reference
We have built a frequency chain which enables to measure the absolute
frequency of a laser emitting in the 28-31 THz frequency range and stabilized
onto a molecular absorption line. The set-up uses an optical frequency comb and
an ultrastable 1.55 m frequency reference signal, transferred from
LNE-SYRTE to LPL through an optical link. We are now progressing towards the
stabilization of the mid-IR laser via the frequency comb and the extension of
this technique to quantum cascade lasers. Such a development is very
challenging for ultrahigh resolution molecular spectroscopy and fundamental
tests of physics with molecules
Determination of the Boltzmann constant by laser spectroscopy as a basis for future measurements of the thermodynamic temperature
In this paper, we present the latest results on the measurement of the
Boltzmann constant kB, by laser spectroscopy of ammonia at 10 ?m. The Doppler
absorption profile of a ro-vibrational line of an NH3 gas sample at thermal and
pressure equilibrium is measured as accurately as possible. The absorption cell
is placed inside a large 1m3 thermostat filled with an ice-water mixture, which
sets the temperature very close to 273.15 K. Analysing this profile, which is
related to the Maxwell-Boltzmann molecular speed distribution, leads to a
determination of the Boltzmann constant via a measurement of the Doppler width
(proportional tosqrt(kBT)). A spectroscopic determination of the Boltzmann
constant with an uncertainty as low as 37 ppm is obtained. Recent improvements
with a new passive thermostat lead to a temperature accuracy, stability and
homogeneity of the absorption cell better than 1 ppm over a day
Absolute frequency measurement of the iodine-stabilized Ar+ laser at 514.6 nm using a femtosecond optical frequency comb.
The frequency of 127I2 hyperfine component a3 of the P(13) 43-0 transition at 514.6 nm has been measured with an optical clockwork based on a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) kHz higher than the value of 582490603.38(15) MHz, adopted by the CIPM in 2003 [T.J. Quinn, Metrologia 40, 103 (2003)] but is in a good agreement with the value measured by R.J. Jones et al [Appl. Phys. B74, 597 (2002)]. In our experiment we used H-maser reference frequency located at BNM-SYRTE Observatoire de Paris and transported to our laboratory by a 43 km optical fibre link
Ultra-stable long distance optical frequency distribution using the Internet fiber network
We report an optical link of 540 km for ultrastable frequency distribution
over the Internet fiber network. The stable frequency optical signal is
processed enabling uninterrupted propagation on both directions. The robustness
and the performance of the link are enhanced by a cost effective fully
automated optoelectronic station. This device is able to coherently regenerate
the return optical signal with a heterodyne optical phase locking of a low
noise laser diode. Moreover the incoming signal polarization variation are
tracked and processed in order to maintain beat note amplitudes within the
operation range. Stable fibered optical interferometer enables optical
detection of the link round trip phase signal. The phase-noise compensated link
shows a fractional frequency instability in 10 Hz bandwidth of 5x10-15 at one
second measurement time and 2x10-19 at 30 000 s. This work is a significant
step towards a sustainable wide area ultrastable optical frequency distribution
and comparison network
Measurement of the Boltzmann constant by the Doppler broadening technique at a 3,8x10-5 accuracy level
In this paper, we describe an experiment performed at the Laboratoire de
Physique des Lasers and dedicated to an optical measurement of the Boltzmann
constant. With the proposed innovative technique, determining comes down to an
ordinary frequency measurement. The method consists in measuring as accurately
as possible the Doppler absorption profile of a rovibrational line of ammonia
in thermal equilibrium. This profile is related to the Maxwell-Boltzmann
molecular velocity distribution along the laser beam. A fit of the absorption
line shape leads to a determination of the Doppler width proportional to
sqrt(kT) and thus to a determination of the Boltzmann constant. The laser
source is an ultra-stable CO2 laser with a wavelength . The absorption cell is
placed in a thermostat keeping the temperature at 273.15 K within 1.4 mK. We
were able to measure with a relative uncertainty as small as 3.8x10-5, which
represents an improvement of an order of magnitude for an integration time
comparable to our previous measurement published in 2007 [1
A widely tunable 10-m quantum cascade laser phase-locked to a state-of-the-art mid-infrared reference for precision molecular spectroscopy
We report the coherent phase-locking of a quantum cascade laser (QCL) at
10-m to the secondary frequency standard of this spectral region, a CO2
laser stabilized on a saturated absorption line of OsO4. The stability and
accuracy of the standard are transferred to the QCL resulting in a line width
of the order of 10 Hz, and leading to our knowledge to the narrowest QCL to
date. The locked QCL is then used to perform absorption spectroscopy spanning 6
GHz of NH3 and methyltrioxorhenium, two species of interest for applications in
precision measurements.Comment: 5 pages, 4 figure
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