Ch. J. Bordé

Six-axis inertial sensor using cold-atom interferometry.

We have developed an atom interferometer providing a full inertial base. This device uses two counterpropagating cold-atom clouds that are launched in strongly curved parabolic trajectories. Three single Raman beam pairs, pulsed in time, are successively applied in three orthogonal directions leading to the measurement of the three axis of rotation and acceleration. In this purpose, we introduce a new atom gyroscope using a butterfly geometry. We discuss the present sensitivity and the possible improvements.

High resolution wavenumber standards for the infrared (Technical Report)

The calibration of high resolution infrared spectra is generally more precise than accurate. This is the case even when they are recorded with Fourier transform interferometers. The present document aims at improving the accuracy of wavenumber measurements in the infrared by recommending a selection of spectral lines as wavenumber standards for absolute calibration in the range from about 4 to about 7000 cm(-1). The uncertainties of these wavenumber standards range from 4+/-1x10(-3) to +/-1x10(-6) cm(-1). Sources of frequency standards, on which the wavenumber determinations are based, are also given.

Quantum Physics Exploring Gravity in the Outer Solar System: The SAGAS Project

We summarise the scientific and technological aspects of the Search for Anomalous Gravitation using Atomic Sensors (SAGAS) project, submitted to ESA in June 2007 in response to the Cosmic Vision 2015–2025 call for proposals. The proposed mission aims at flying highly sensitive atomic sensors (optical clock, cold atom accelerometer, optical link) on a Solar System escape trajectory in the 2020 to 2030 time-frame. SAGAS has numerous science objectives in fundamental physics and Solar System science, for example numerous tests of general relativity and the exploration of the Kuiper belt. The combination of highly sensitive atomic sensors and of the laser link well adapted for large distances will allow measurements with unprecedented accuracy and on scales never reached before. We present the proposed mission in some detail, with particular emphasis on the science goals and associated measurements and technologies.

Heterodyne saturation spectroscopy through frequency modulation of the saturating beam

Abstract We present a new spectroscopic method to detect saturated absorption signals. Its principle lies in a high frequency modulation of the saturation beam and a detection of the induced modulation of the probe combined with a frequency offset of the saturation beam. This method, which directly provides a dispersion-like lineshape, is very effective to increase the sensitivity close to the shot-noise limit and to cancel the various backgrounds.

Molecular interferometry experiments

Abstract We have performed interferometry experiments with de Broglie waves of the I2 molecule, with an interferometer comprising four laser waves as molecular beam splitters. We have investigated how this interferometer can be tuned by communicating a different velocity to the molecules along each arm. A comparison with the neutron interferometer is outlined.

Intensities of hyperfine components in saturation spectroscopy

Abstract A theory is presented for the intensities of hyperfine components in saturation spectroscopy. We use a diagrammatic approach to nonlinear processes to derive closed-form formulas for the intensities of recoil doublets and of Doppler-generated level crossings. We discuss the influence of the terms introduced by hyperfine coherences in saturation spectroscopy. We also demonstrate spectroscopic stability when the hyperfine splittings are negligible. A catalog of simple formulas is given in view of applications to current spectroscopy and is illustrated by recent examples, including Doppler-free polarization spectroscopy. The extension to other sub-Doppler techniques such as two-photon Doppler-free spectroscopy is outlined.

Ultrahigh-resolution saturation spectroscopy using slow molecules in an external cell

We present the narrowest molecular lines so far recorded in the 10 µm spectral region. A linewidth of 80 Hz (HWHM) has been obtained for theP(39)A13(−) line of OsO4, by selecting slow molecules (Teff=0.6 K) in saturation spectroscopy at low laser fields (30 nW) and low pressures (2 × 10−6 Torr). In these conditions, the contribution of the fast molecules is greatly reduced because of the finite size of the beam. This method, applied previously to methane at 3.39 µm, is used for the first time in an external cell and improves by a factor 8 the best resolution of our spectrometer. Heterodyne detection and double frequency modulation have been necessary to extract a signal at a contrast of only 10−6. The physical ideas concerning this regime are described and a detailed analysis of the line shape is given.

Supersonic beam spectroscopy of low J transitions of the ν3 band of SF6: Rabi oscillations and adiabatic rapid passage with a CW laser

Abstract The P(3) and P(4) manifolds of the ν3 band of SF6 have been observed in a supersonic beam with a bolometric detection. The influence of the laser beam divergence on the excitation efficiency has been studied. Rabi oscillations are observed when the wavefront is flat in the interaction region whereas only adiabatic rapid passage occurs when the molecules see a curved wavefront.

Frequency measurements of hyperfine splittings in ground rovibronic states of I2 by stimulated resonant Raman spectroscopy

Abstract:Measurements of hyperfine splittings in the ground electronic state of have been performed by stimulated Raman spectroscopy. An argon laser emitting at 514.5 nm, drives the coherence between hyperfine levels of the J”=13 or J”=15 rotational levels of the ground vibronic state, via resonant excitation of the hyperfine transitions of the optical resonances (43-0) P(13) or R(15). We study the influence of the various experimental parameters on the line shape: the beam geometry, the laser modulation spectrum, the laser power, the molecular frequency shifts. We show that only beam aberrations can give rise to a significant asymmetry of the line shape, which contributes to an error in the determination of the resonance frequency. From a theoretical expression of the line shape taking into account the beam geometry, a detailed study of this error is performed. The theoretical predictions and the experimental results are in very good agreement. From the measurements, improved sets of hyperfine interaction constants for the molecule have been calculated for J”=13 and J”=15. These constants are identical for both levels, except for quadrupole coupling constant eqQ which exhibits a J-dependence, which we attribute to the centrifugal distortion of the molecule.

Absolute frequency determination of super-narrow CO2 saturation peaks observed in an external absorption cell

Abstract We have succeeded in observing very narrow saturation resonances (hwhm=2.1 kHz) of room temperature CO2 by monitoring directly the absorption of a CO2 laser beam in an external absorption cell. Through successive recordings of the CO2 lines and OsO4 lines of known absolute frequency, we have been able to perform a preliminary determination of the frequencies of three CO2 lines (respectively P(14) and R(10) of the 10.4 μm band) with an accuracy of the order of one kilohertz. A good agreement is found with previous measurements based on the saturated 4.3 μm fluorescence method. The main interest of this new method is to provide values for the frequencies in the free-flight regime.