I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric Inertial Sensors in Reduced Gravity

The accuracy and precision of current atom-interferometric inertialsensors rival state-of-the-art conventional devices using artifact-based test masses . Atomic sensors are well suited for fundamental measurements of gravito-inertial fields. The sensitivity required to test gravitational theories can be achieved by extending the baseline of the interferometer. The I.C.E. (Interf\'erom\'etrie Coh\'erente pour l'Espace) interferometer aims to achieve long interrogation times in compact apparatus via reduced gravity. We have tested a cold-atom source during airplane parabolic flights. We show that this environment is compatible with free-fall interferometric measurements using up to 4 second interrogation time. We present the next-generation apparatus using degenerate gases for low release-velocity atomic sources in space-borne experiments

Stabilisation de fréquence de laser Nd:YAG pour applications spatiales

Long term stabilised lasers are used in a multitude of metrological applications ; in the last few years their prospective use for space applications has been growing, fundamental physics experiments, geodesy...This work concerns the stable lasers for the LISA project; in view of the potential space application, many criteria- compactness, mechanical stability, robustness and reliability- must be satisfied.The possible references useful for the long term (iodine) and the short term (FP cavity) time intervals will be described together with their principal limitations. The discussion leading to their choice is coupled with the analysis of the stabilisation techniques to be implemented (PDH, Tilt-Locking, Modulation transfer).Among the stabilisation techniques, the state of the art Pound-Drever-Hall (PDH) technique will be compared to the DC, active components poor Tilt Locking in the case of a monolithic Fabry-Perot reference.For each technique and each reference, the description of noise sources and the expected error signals will be shown trhough simulation. Theoretical performances on the long term and quantum efficiencies will be compared for different techniques.The second part gives the schematic principles of the experiences and the results obtained for lasers stabilised on Fabry-Perot oscillators and molecular iodine. To calibrate the Fabry-Perot drifts, its resonance frequency will be measured vs. the molecular transition, this will coupled with analytical and numerical solutions to control the length of this mechanical reference.Finally in the appendices details about noise order of magnitudes for LISA (leading to laser specification), a theoretical overview of gravitational waves as well as different simulations and calculations will be shown.Les lasers stabilisés à long terme sont utilisés dans de nombreux domaines en métrologie, leur incursion dans les applications spatiales se précise depuis quelques années, missions de physique fondamentale, géodésie... Ce travail concerne les lasers stables pour le projet LISA (détection spatiale des ondes de gravitation, mission prévue dans 10 ans); en vue de cette application spatiale, les montages doivent satisfaire plusieurs critères: compacité, stabilité mécanique, robustesse et fiabilité. Les références utilisables pour l'asservissement long terme (iode, chapitre 3) et court terme (cavité de Fabry-Pérot, chapitre 4) sont décrites, ainsi que leurs limitations principales. L'analyse et le choix de ces références de stabilisation seront couplés avec le choix des techniques de stabilisation (PDH, Tilt-Locking, Modulation Transfer). Dans les techniques de stabilisation, celle de Pound-Drever-Hall (PDH), un classique en matière de configuration, est comparée au Tilt-Locking, une technique continu et peu consommatrice en énergie, dans le cas d'une référence Fabry-Perot monolithique. Les calcules théorique pour chaque technique et chaque type de référence ammeneront à une description des sources de bruit et à une simulation des signaux d'erreur attendus. Les performances théoriques sur le long terme et les efficacités quantiques sont intercomparées. La deuxième partie, présentera les montages expérimentaux et les résultats obtenus, pour des lasers stabilisés sur Fabry-Perot et sur l'Iode moléculaire. Pour calibrer les dérives de fréquence du Fabry-Perot, sa fréquence de résonance sera mesurée par rapport à celle de la molécule, ce qui permettra de présenter des solutions obtenues analytiquement et numériquement pour l'asservissement en longueur de cette référence mécanique. En appendices, les détails de dimensionnement des bruits de LISA conduisant aux spécifications des lasers, le rappel théorique des ondes de gravitation ainsi que divers simulations de calculs effectués

Caveats and pitfalls of high energy UV laser operation on ground

During the Aeolus laser and instrument transmitter development it was shown that atmosphere quality was one major limiting factor for high energy UV laser operation at ambient pressure. As already proven in literature operation can only be safely obtained in the presence of oxygen ([1] to [6]). Furthermore, air quality has to be adequately controlled and monitored to ensure that no catastrophic event occurs. On-line qualitative (no/no-go discriminator) can be obtained using fluorescence monitoring of the laser beam, while GC-MS remains the technique of choice to quantitatively evaluate suitability of air supply a priori. LIC testing is in the process of being adapted to trace contaminant evaluation. Finally, the formation of laser generated absorbing features is described, during air irradiation. The potential root causes of these absorbing dot-like features are explored, using optical measurements, microscopic inspections and chemical analysis. Current results indicate organic deposits associated with metallic particles and a presence of phosphate

Frequency stabilised Nd : YAG lasers for space applications

NICE-BU Sciences (060882101) / SudocSudocFranceF

Laser-induced molecular contamination de-risking activity for the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) will be the first space-based gravitational wave observatory. LISA uses continuous-wave, infrared laser beams propagating among three widely separated spacecrafts to measure their distances with picometer accuracy via time-delay interferometry. These measurements put very high demands on the laser wavefront and are thus very sensitive to any deposits on laser optics that could be induced by laser-induced molecular contamination (LIMC). In this work, we describe the results of an extensive experimental test campaign assessing LIMC related risks for LISA. We find that the LIMC concern for LISA, even considering the high demands on the laser wavefront, may be greatly reduced compared to that observed at shorter wavelengths or with pulsed laser radiation. This result is very promising for LISA as well as for other space missions using continuous-wave, infrared laser radiation, e.g., in free space laser communication or quantum key distribution

Molecular contamination testing with continuous-wave laser radiation at 1064 nm: de-risking activity for the LISA space mission

We investigate effects of laser-induced contamination (LIC) with contaminant materials and laser parameters relevant for the LISA space mission. To accelerate outgassing and a possible deposit formation, the contaminant materials have been heated to a temperature of up to 100 °C (nominal operating temperature of 20° C), and LIC tests were performed with a laser power density of up to 300 W/cm2 (to be compared with expected 125 W/cm2). Neither in-situ measurements (laser transmission, polarization and wavefront), nor a careful microscopic inspection of the optical surfaces after the LIC tests showed indications of a laser-induced deposit formation. Condensation on optical surfaces could be observed. This is cautiously encouraging for LISA and indicates that the LIC concern may be reduced compared to what observed at shorter wavelength or with pulsed laser radiation

High-power and frequency-stable ultraviolet laser performance in space for the wind lidar on Aeolus

Global acquisition of atmospheric wind profiles using a spaceborne direct-detection Doppler wind lidar is being accomplished following the launch of European Space Agency's Aeolus mission. One key part of the instrument is a single-frequency, ultraviolet laser that emits nanosecond pulses into the atmosphere. High output energy and frequency stability ensure a sufficient signal-to-noise ratio of the backscatter return and an accurate determination of the Doppler frequency shift induced by the wind. This Letter discusses the design of the laser transmitter for the first Doppler wind lidar in space and its performance during the first year of the Aeolus mission, providing valuable insights for upcoming space lidar missions

ESA’s Spaceborne Lidar Mission ADM-Aeolus; Recent Achievements and Preparations for Launch

Within ESA’s Living Planet Programme, the Atmospheric Dynamics Mission (ADM-Aeolus) was chosen as the second Earth Explorer Core mission in 1999. It shall demonstrate the potential of high spectral resolution Doppler Wind lidars for operational measurements of wind profiles and their use in Numerical Weather Prediction (NWP). Spin-off products are profiles of cloud and aerosol optical properties. ADM-Aeolus carries the novel Doppler Wind lidar instrument ALADIN. Recently the two ALADIN laser transmitters were successfully qualified and delivered for further instrument integration. The instrument delivery will follow later this year and the satellite qualification and launch readiness is scheduled for 2016. In February 2015, an Aeolus Science and Calibration and Validation (CAL/VAL) Workshop was held in ESA-ESRIN, Frascati, Italy, bringing industry, the user community and ESA together to prepare for the Aeolus Commissioning and Operational Phases. During the Workshop the science, instrument and product status, commissioning phase planning and the extensive number of proposals submitted in response to the Aeolus CAL/VAL call in 2014 were presented and discussed. A special session was dedicated to the Aeolus CAL/VAL Implementation Plan. In this paper, the Aeolus mission, status and launch preparation activities are described

ESA’s Spaceborne Lidar Mission ADM-Aeolus; Recent Achievements and Preparations for Launch

Within ESA’s Living Planet Programme, the Atmospheric Dynamics Mission (ADM-Aeolus) was chosen as the second Earth Explorer Core mission in 1999. It shall demonstrate the potential of high spectral resolution Doppler Wind lidars for operational measurements of wind profiles and their use in Numerical Weather Prediction (NWP). Spin-off products are profiles of cloud and aerosol optical properties. ADM-Aeolus carries the novel Doppler Wind lidar instrument ALADIN. Recently the two ALADIN laser transmitters were successfully qualified and delivered for further instrument integration. The instrument delivery will follow later this year and the satellite qualification and launch readiness is scheduled for 2016. In February 2015, an Aeolus Science and Calibration and Validation (CAL/VAL) Workshop was held in ESA-ESRIN, Frascati, Italy, bringing industry, the user community and ESA together to prepare for the Aeolus Commissioning and Operational Phases. During the Workshop the science, instrument and product status, commissioning phase planning and the extensive number of proposals submitted in response to the Aeolus CAL/VAL call in 2014 were presented and discussed. A special session was dedicated to the Aeolus CAL/VAL Implementation Plan. In this paper, the Aeolus mission, status and launch preparation activities are described