Anthony BERCY will defend his PhD thesis , entitled “Ultrastable optical fiber link : multiple-users dissemination, study of fundamental and technological limits and new applications”. His thesis work was accomplished within a collaboration between LPL and SYRTE. His thesis grant has been co-funded by FIRST-TF.
The ITU World Radiocommunication Conference (WRC-15), currently in session in Geneva from 2 to 27 November, has decided that further studies are required on the impact and application of a future reference time-scale, including the modification of coordinated universal time (UTC) and suppressing the so-called “leap second”.
Alexis BONNIN will defend his PhD thesis , entitled “Dual-Species Atom Interferometry and Applications to Inertial Measurements”, which work was accomplished in ONERA . The defense will take place on Monday, 23 of November 2015 at 14:00 in Laboratoire Aimé Cotton (Salle Balmer), Orsay.
In the emerging issue of testing the Equivalence Principle with cold atom inertial sensors, this thesis focuses on the realization and the characterization of a simultaneous dual-species atom interferometer (87Rb & 85Rb) which allows to measure the diﬀerential acceleration in an extremely sensitive way. The Mach-Zehnder type atom interferometer relies on the simultaneous handling of atomic wave-packets with stimulated Raman transitions. The laser system is based on the frequency doubling of a single laser source at 1560 nm. All the required laser frequencies for handling both isotopes (trapping, cooling, selection, interferometry and detection) are generated by phase modulating this source. A detailed modeling of the interferometer’s inertial responses and an analysis of a method to extract the diﬀerential phase were carried out. The diﬀerential acceleration measurement led to an atom based test of the Weak Equivalence Principle of η( 87Rb, 85Rb) = (1.3 ± 3.2) × 10− 7, at the state-of-the-art. The simultaneous aspect of the experiment allowed to highlight for the ﬁrst time common mode vibration noise rejection with two diﬀerent atomic species, a rejection factor of 50 000 being currently achieved. The current performance of the instrument exhibits a sensitivity on the diﬀerential acceleration of 1.23 × 10− 7 g/sqrt(Hz) and a resolution of 2 × 10− 9 g for integration times lower than few hours. Finally, innovative operating modes of dual-species atom interferometers for on-board acceleration measurements are explored.
Fabien Théron will defend his PhD thesis , entitled “Development of a cold atom gravity gradiometer and a telecom doubled laser device for onboard applications”, which work was accomplished in ONERA . The defense will take place on Friday, Friday, 27 of November 2015 at 14:00 in Institut d’Optique Graduate School (Auditorium), Palaiseau.
This thesis presents the development of the experimental setup allowing the measurement of two gravity gradient components and the gravity acceleration. These quantities are resulted from the measuring of rubidium cold atoms acceleration, in free fall in vacuum, by atom interferometry. For gradiometry, the differential measurement is realized between two atomic clouds spatially separated. For the measurement of vertical gradient, the use of mobile optical lattices allows to get two atom clouds from a single atomic source.
This work presents the setting up of the complete device, in particular with the built of the vaccum chamber, laser and micro-wave systems. Lasers are based on frequency-doubled telecom technology, which allows to obtain compact and robust systems, dedicated for onboard applications. The innovative laser architecture allows to combine atom interferometry and optical lattices, while minimizing the amount of components. The laser noise has been characterized, and limits the single shot gravimetric sensitivity to 10-9 g, the single shot differential sensitivity to 10-10 g, and the single shot gradiometric sensitivity to 38 E.
Indranil DUTTA will defend his PhD thesis , entitled “Stability Improvement of a Sagnac Cold Atom Interferometer: towards Continuous Operation”, which work was accomplished in SYRTE under the supervision of Arnaud Landragin. The defense will take place on Friday, 20 of November 2015 at 14:30 in Paris Observatory (Salle de l’IAP).