Defenses – Seminars

Homepage > Research & innovation > Scientific events > Defenses – Seminars

Defenses – Seminars

December 6th, 2024 at 09:30 - PhD defense by Maxime Pesche: “Atteindre le nano-g avec un gravimètre absolu à atomes froids”

Friday, December 6th 2024 at 9:30 a.m., Maxime Pesche will defend his PhD thesys: “Atteindre le nano-g avec un gravimètre absolu à atomes froids”, prepared at SYRTE and under the supervision of Franck Pereira Dos Santos et Sébastien Merlet. The defense will take place in Salle Dénisse, accessible by the Observatory of Paris, 77 avenue Denfert Rochereau, 75014 Paris
November 21, 2022 at 14:00 - PhD defense by Mads Tønnes: “Understanding and exploiting metrological fiber networks for Sagnac sensing, frequency dissemination and geosensing”

Mads Tønnes will defend his thesus on November 21st, 2022 at 2:00 p.m., entitled: “Understanding and exploiting metrological fiber networks for Sagnac sensing, frequency dissemination and geosensing”, prepared at the University of Paris Sciences et Lettres and under the supervision of Sébastien Bize and Paul-Éric Pottie. The defense will take place in the Amphithéâtre de l’IAP, accessible by the Observatory of Paris, 77 avenue Denfert Rochereau, 75014 Paris).
September 5, 2022 at 14:00 - PhD defense by Zhibin Yao: “Atom interferometry with Bose-Einstein Condensate: Toward a determination of fine structure constant”

Zhibin Yao will defend his thesis on September 5, 2022 at 14:00, entitled “Atom interferometry with Bose-Einstein Condensate: Toward a determination of fine structure constant”, prepared at the Sorbonne University and under the direction of Saïda Guellati-Khélifa at LKB.
The defense will be in English and will take place in Amphi Durand (Campus Pierre et Marie Curie). The defense will be also streamed on Zoom :
Zhibin Yao_PhD_Defense_“Atom interferometry with Bose-Einstein Condensate: Toward a determination of fine structure constant”
April 13th, 2022 at 9:30 a.m - PhD defense by Shuo Zhang: “Spectral Hole Burning for Ultra-stable Lasers”
Shuo Zhang will defend her thesis on April 13th, 2022 at 9:30 a.m., entitled: “Spectral Hole Burning for Ultra-stable Lasers”, prepared at the University of Paris Sciences et Lettres in collaboration with the SYRTE and under the supervision of Yann Le Coq, Bess Fang-Sortais and Signe Seidelin.
The defense will take place at the Salle du Conseil of the Observatoire de Paris (77 avenue Denfert Rochereau, 75014 Paris). The defense will be streamed on Zoom : Shuo Zhang’s PhD defense : Spectral Hole Burning for Ultra-stable Lasers
Programme
July 7th, 2021 - PhD defense by Lucas Groult: “Conception d’un piège de Paul microfabriqué pour le développement d’une horloge optique compacte, à ion piégé Yb+”

Lucas Groult will defend his thesis on July 7th 2021, entitled: “Conception d’un piège de Paul microfabriqué pour le développement d’une horloge optique compacte, à ion piégé Yb+”, prepared at the University of Bourgogne Franche-Comté, in collaboration with FEMTO-ST and under the supervision of Yann Kersalé.

The defense will be in the amphithéâtre Jules Haag – ENSMM – 26, Rue de l’Epitaphe – Besançon.
May 31st, 2021 - PhD defense by Alexandre Bouvier: “Studies on the mid-term effects of the Double-Modulation CPT clock”.

Alexandre Bouvier will defend his thesis on May 31st, 2021, entitled: “Studies on the mid-term effects of the Double-Modulation CPT clock”, prepared at the University of Paris Sciences et Lettres and under the supervision of Stéphane Guérandel.

The defense, in French, will be in the salle du Levant of the Observatoire de Paris (77 avenue Denfert Rochereau, 75014 Paris).
March 15, 2021 - PhD defense by Héctor Alvarez Martinez: "Characterization of optical frequency comb based measurements and spectral purity transfer for optical atomic clocks".

Héctor Alvarez Martinez will defend his thesis on March 15, 2021, entitled: “Characterization of optical frequency comb based measurements and spectral purity transfer for optical atomic clocks”, prepared at Sorbonne University in collaboration with the University of Madrid Carlos III and under the supervision of Yann Le Coq and Rodolphe Le Targat.

The defense will take place on March 15, 2021 at 2 p.m., at the Salle du Levant of the Observatoire de Paris. The defense will be streamed on the internet : YouTube channel for the live streaming
September 21, 2020 - PhD defense of Joannes Barbarat: “Development of an IR & visible laser source, compact, fiber, stabilized in frequency”

Joannes Barbarat will defend his thesis on September 21, 2020, entitled: “Development of an IR & visible laser source, compact, fibered, frequency stabilized”, prepared at the University of Paris Sciences et Lettres and under the supervision of Philip Tuckey and Ouali Acef.
20th of Decembre 2019 (Paris) – PhD defense of Nicolas Galland: “Towards optomechanical systems and high precision measurements with rare-earth doped crystals”

Nicolas GALLAND will defend his thesis the 20th of December 2019 in Paris Paris, on: “Towards optomechanical systems and high precision measurements with rare-earth doped crystals”, prepared at Institut NEEL and SYRTE under the supervision of Signe Seidelin and Yann Le Coq.

The defense will take place the 20th décembre à 2pm, in the IAP amphitheatre , at Observatoire de Paris (77 avenue Denfert Rochereau). The defense will be in French.
6th Decembre 2019 (Paris) – PhD defense of Valentin Cambier "Mercury optical lattice clock exploiting a 2D-MOT : lifetime of the 3P0 state and frequency measurement"

Valentin Cambier will defend his PhD thesis the 6th of December 2019 at 2pm on “Mercury optical lattice clock exploiting a 2D-MOT : lifetime of the 3P0 state and frequency measurement”, prepared at SYRTE under the supervision of Sébastien Bize.

The defense will take place in the Salle Cassini of the Observatoire de Paris.
12th december 2019 (Meudon) – PhD defense of Amina Saadani "Bidimensional crystal electrodes for high quality factor piezoelectric micro/nano-resonators"

Amina Saadani will defend her PhD thesis the 12th of December 2019 et 2.30 pm on “Bidimensionnal crystal electrodes for high quality factor piezoelectric micro/nano-resonators”, prepared at ONERA under the supervision of Fabrice Sthal (FEMTO-ST), Olivier Le Traon and Pierre Lavenus (ONERA/DPHY).

The defendse will be in “salle Ay-02-63” of the ONERA center in Meudon, 8 rue des Vertugadins, 92190 Meudon
Please contact sylvie.nicolle-douet AT onera.fr about the formalities necessary to enter the premises.
9th of December (Châtillon) - PhD defense of Paul Chapellier "piezo-electric MEMS for Time and Frequency applications"

Paul Chapellier will defend his PhD thesis the 9th of December at 2pm on “piezo-electric MEMS for Time and Frequency applications”, prépared at ONERA under the supervision of Bernard DULMET (FEMTO-ST) and Pierre Lavenus (ONERA/DPHY).

The defense wil be in “salle Contensou” at the ONERA centerin Châtillon, 29 avenue de la Division Leclerc, 92320 CHATILLON
Please contact sylvie.nicolle-douet@onera.fr about the formalities necessary to enter the premises.
18th of October 2019 (Paris) - PhD defense of Romain CALDANI: "Atom interferometry for simultaneous measurement of g and its vertical gradient"

Romain CALDANI will defend his thesis on 18th of October 2019 at 10:00 am on the subject “Atom interferometry for simultaneous measurement of g and its vertical gradient”, realized at SYRTE under the supervision of Franck Pereira Dos Santos and Sébastien Merlet.

The defense will take place in the salle de l’Atelier of the Observatoire de Paris (77 avenue Denfert Rochereau, 75014 Paris).
15th of October 2019 (Paris) - PhD defense of Romain KARCHER: "Implementation of an ultra-cold atom source to improve the accuracy of an atomic gravimeter"

Romain KARCHER will defend his thesis on 15th of October 2019 at 2:00 pm on the subject “Implementation of an ultra-cold atom source to improve the accuracy of an atomic gravimeter”, realized at SYRTE under the supervision of Franck Pereira Dos Santos and Sébastien Merlet.

The defense will take place in the amphitheater of the Institut d’Astrophysique de Paris (IAP), accessible through the Observatoire de Paris at 77 avenue Denfert Rochereau, 75014 Paris.
23th of September 2019 (Palaiseau) - PhD defense of Isadora PERRIN: "Développement expérimental d’un capteur inertiel multi-axe à atomes froids hybride embarquable"

Isadora PERRIN will defend her thesis on 23th of September 2019 at 2:00 pm on the subject “Développement expérimental d’un capteur inertiel multi-axe à atomes froids hybride embarquable”, realized at ONERA under the supervision of François Nez (LKB) and the supervision of Yannick Bidel (ONERA).

The defense will take place in the Auditorium of Institut d’Optique Graduate School (2 avenue Augustin Fresnel, Palaiseau).
23th of September 2019 (Paris) - PhD defense of Léo MOREL: "High sensitivity matter-wave interferometry: towards a determination of the fine structure constant at the level of 10E-10"

Léo MOREL will defend his thesis on 23th of September 2019 at 2:00 pm on the subject “High sensitivity matter-wave interferometry: towards a determination of the fine structure constant at the level of 10E-10”, realized at LKB, under the direction of Saïda Guellati-Khelifa and Pierre Cladé.

The defense will take place in the IMPMC conference room (corridor 22/23, 4th floor, room 401), Jussieu campus of Sorbonne Université.

The defense will be in English.

Abstract:

The fine structure constant can be determined from the measurement of the ratio h/m between the Planck constant, h, and the mass of an atom, m. The comparison of the experimental value of the anomalous magnetic moment of the electron or the muon with their theoretical values predicted by the Standard Model using this value of the fine structure constant allows a very precise test of this model.
My thesis work focused principally on the measurement of the h/m ratio of rubidium-87 using a new experimental device. We installed the laser device for atom interferometry, to interrogate a cloud of cold atoms produced by optical molasses. Combining an interferometer using Raman transitions and the Bloch oscillation technique, we demonstrated an unprecedented sensitivity on the measurement of h/m corresponding to a relative statistical uncertainty of 8.5 x 10 -11 in 48 hours of integration, or 4.3 x 10 -11 on the fine structure constant.
This sensitivity has allowed us to experimentally study a variety of systematic effects. We simultaneously carried out modelling work that contributed to the implementation of protocols to compensate for the biases induced by systematic effects. We present a preliminary assessment of the error budget associated with these effects.
17th of September 2019 (Paris) - PhD defense of Mengzi HUANG: "Spin squeezing and spin dynamics in a trapped-atom clock"

Mengzi HUANG will defend his thesis on 17th of September 2019 at 2:00 pm on the subject “Spin squeezing and spin dynamics in a trapped-atom clock”, realized at SYRTE and LKB under the supervision of Carlos Garrido Alzar and Jakob Reichel.

The defense will take place in the amphitheater of the Institut d’Astrophysique de Paris (IAP).

The defense will be in English, in front of a jury composed of Monika Schleier-Smith, Morgan Mitchell, Ludovic Pricoupenko and Rodolphe Boudot.

Abstract:

Atomic sensors are among the best devices for precision measurements of time, electric and magnetic fields, and inertial forces.
However, all atomic sensors that utilise uncorrelated particles are ultimately limited by quantum projection noise (QPN), as is already the case for state-of-the-art atomic clocks. This so-called standard quantum limit (SQL) can be overcome by employing entanglement, a prime example being the spin-squeezed states. Spin squeezing can be produced in a quantum non-demolition (QND) measurement of the collective spin, particularly with cavity quantum electrodynamical (QED) interactions.

In this thesis, I present the second-generation trapped-atom clock on a chip (TACC) experiment, where we combine a metrology-grade compact clock with a miniature cavity-QED platform to test quantum metrology protocols at a metrologically-relevant precision level. In a standard Ramsey spectroscopy, the stability of the apparatus is confirmed by a fractional frequency Allan deviation of 6E-13 at 1 s. We demonstrate spin squeezing by cavity QND measurement, reaching 8 (1) dB for 1.7E4 atoms, currently limited by decoherence due to technical noise. Applying these spin-squeezed states in the clock measurement is within reach.

Cold collisions between atoms play an important role at this level of precision, leading to rich spin dynamics. Here we find that the interplay between cavity measurements and collisional spin dynamics manifests itself in a quantum amplification effect of the cavity measurement. A simple model is proposed, and is confirmed by initial measurements. New experiments in this direction may shed light on the surprising many-body physics in this sytem of interacting cold atoms.
15th of July 2019 (Villetaneuse) - PhD defense of Dang Bao An TRAN: "Widely tunable and SI-traceable frequency-comb-stabilised mid-infrared quantum cascade laser: application to high precision spectroscopic measurements of polyatomic molecules"

Dang Bao An TRAN will defend his thesis on 15th of July 2019 at 10:30 am on the subject “Widely tunable and SI-traceable frequency-comb-stabilised mid-infrared quantum cascade laser: application to high precision spectroscopic measurements of polyatomic molecules”, realized at LPL, under the direction of Anne Amy-Klein and Benoît Darquié.

The defense will take place in Copernic Amphitheatre – Institut Galilée, Université Paris 13 (access).

The defense will be in English.

=> Abstract and venue information.
28th of June 2019 (Villetaneuse) - HDR defense of Vincent RONCIN: "Self-pulsating semiconductor lasers: Applications in optical communications and frequency Metrology"

Vincent RONCIN will defend his “habilitation à diriger des recherches” on 28th June 2019 at 2:00 pm on the subject “Self-pulsating semiconductor lasers: Applications in optical communications and frequency Metrology”.

The defense will take place at Université Paris 13 (99, av. J.-B. Clément, 93430 Villetaneuse) in Copernic amphitheater (Institut Galilée).

Abstract:

This report on research works of M. Vincent Roncin is proposed for french diploma “Habilitation à Diriger des Recherches”. The first part is dedicated to its activity at Foton laboratory (Lannion) in the framework of optical functions for telecom applications. It deals with the study of Passive Mode Locked Lasers for Optical Clock Recovery at high bit rates, and with internal locking dynamics in multimode semiconductor lasers.

The second part presents its activity in LPL (Villetaneuse) in the framework of metrological optical links over optical fiber. It deals with stabilized optical amplification based on Brillouin scattering in optical fiber. The last part concerns its activity in LPL on the stabilization of compact Frequency Combs based on passive mode locked lasers, for frequency metrology applications.
28th of June 2019 (Paris) - HDR defense of Rémi GEIGER: "Atom interferometry: from fundamental physics to precision inertial measurements"

Rémi GEIGER will defend his “habilitation à diriger des recherches” on 28th June 2019 at 2:00 pm on the subject “Atom interferometry: from fundamental physics to precision inertial measurements”.

The defense will take place at Observatoire de Paris (77 av. Denfert-Rochereau, Paris 14ème) in Salle Cassini, Bâtiment Perrault.

Abstract:

Interferometry with matter waves dates back to the first ages of quantum mechanics as the concept of matter waves played a key role in the development of the quantum theory. Performing interference experiments with various types of matter-waves has driven the efforts of several communities working with electrons, neutrons, atoms, molecules, or anti-matter. The field of atom interferometry has developed rapidly within the atomic physics community and even more since the advent of laser cooling techniques in the 1980s, which offers a high level of control. Cold-atom interferometers are nowadays studied by more than 40 research laboratories in the world and developed in several companies. They address a large panel of applications in tests of fundamental physics, metrology, geosciences, inertial navigation or gravitational wave astronomy. In this presentation, I will describe some of my research projects related to the measurements of gravitational and inertial effects with cold-atom interferometers within the atom interferometry and inertial sensor team of SYRTE at Paris Observatory.
8th of February 2019 (Marseille) - PhD defense of Mathieu Collombon: "Three-photon dark resonance in a cloud of stored Calcium ions"

Mathieu COLLOMBON will defend his thesis on 8th of February 2019 at 11:00 am on the subject “Optimization of a force sensor based on ultracold atoms trapped in a vertical lattice”, realized at PIIM, under the direction of Martina Knoop.

The defense will take place in the “Thesis room”, on the St-Jérôme campus in Marseille.

You are also very welcome to the traditionnel buffet after the defense, that will take place at the service 322 (Lab’s cafeteria).

Abstract:

The work presented in this thesis describes the complete experimental set-up and approach to realize three-photon coherent population trapping in a cloud of radiofrequency confined Calcium ions. The realization of such a population trapping relies on a stringent conditions of the phase relationship between the three lasers involved in the interrogation process, and also their spectral linewidths. Our experimental approach is based on the optimization of the performance of a frequency-stabilized titanium-sapphire laser at 411 THz (729nm) at the 10−14 level, in term of relative frequency uncertainties. This laser’s frequency stability is subsequently transfered to a optical frequency comb by means of a phase-locked loop. Then the two other lasers involved (866 nm and 794 nm) are phase-locked to the optical frequency comb with the same technique. This work describes the transfer method along with its measured performances. With all the three lasers sharing the same ultra-stable frequency reference we have been able to experimentally observe for the first time a 3-photon dark resonance in the fluorescence spectra of the 40Ca+, signature of a coherent population trapping in a 3-photon scheme. The dependence of this resonance at experimental parameters, such as laser powers, laser detunings and local magnetic field, have been studied and are presented in this work. The preliminary results have allowed to explain the behaviour of the dark resonance and explored conditions for the use of the 3-photon dark line as a THz frequency standard.
20th of December 2018 (Paris) - PhD defense of Xavier Alauze: "Optimization of a force sensor based on ultracold atoms trapped in a vertical lattice"

Xavier ALAUZE will defend his thesis on 20th of December 2018 at 2:00 pm on the subject “Optimization of a force sensor based on ultracold atoms trapped in a vertical lattice”, realized at SYRTE, under the direction of Franck Pereira dos Santos.

The defense will take place in the “Institut d’Astrophysique de Paris” (IAP) amphitheater, in front of a jury composed of Vincent Josse, Athanasios Laliotis, Jean-François Roch et Alice Sinatra.

The defense will be in french.

You are also very welcome to the traditionnel buffet after the defense, that will take place in the restaurant of the Observatoire de Paris.

Abstract:

The aim of the ForCa-G project (for Casimir-Polder Force and Gravitation) is to measure short range forces between an atom and a macroscopic surface. Our force sensor involves 87Rb atoms trapped in a vertical optical lattice where two-photon Raman transitions allow to create a coherent superposition of spatially separated states and thus realize an atom interferometer to measure the variation of the potential in the vertical direction. Given the high position dependence of atom-surface interaction forces, a very high spatial resolution of the sensor is required. A micrometric spatial resolution of the force measurement is achieved by reducing the size of the atomic source using evaporative cooling. The relative sensitivity, obtained for the measurement of the gravitational force, of 5.10-6 at 1 s, which averages down to 8.10-8 in 1 h, is at the state of the art for such a spatial resolution. Improving this resolution implies an increase in atomic density. A study of atomic interactions is then carried out in the particular conguration of our trapped atom interferometer where we have a coherent control over the wavepackets overlap. In order to improve the spatial resolution further, we will select a single eigenstate of the system. For that, we lift the degeneracy of the energy increment between adjacent wells using a super-lattice.
14th of December 2018 (Villetaneuse) - PhD defense of Amine Chaouche Ramdane: "Experimental developments for the characterization and stabilization of semiconductor self-pulsed laser sources for frequency metrology applications"

Amine Chaouche Ramdane will defend his thesis on 14th of December 2018 at 1:30 pm on the subject “Experimental developments for the characterization and stabilization of semiconductor self-pulsed laser sources for frequency metrology applications”, realized in LPL, under the supervision of Frédéric Du Burck and co-supervised by Vincent Roncin.

The defense will take place in Amphi. D – Institut Galilée at Université Paris 13, 99 av. J.B. Clément 93430 Villetaneuse, in front of a jury composed of Saïda Guellati, Alexandre Shen, Didier Erasme, Loïc Morvan, Pascal Besnard, Daniel Bloch, Frédéric Du Burck, Vincent Roncin.

Abstract:

This PhD thesis focuses on the development of instrumentation for the characterization and stabilization of mode-locked laser sources at 1.55 µm for applications in frequency metrology or stability applications in the field of optical telecommunications.
Two characterization tools based on commercial components were developed with the aim to transfer the frequency stability from a metrological source to tunable sources (ECLD). In both cases, stability transfers over tens of nanometres are demonstrated at the level of 10 -12 . The detailed analysis of those setups shows the limitations resulting from residual amplitude and polarization modulations due to modulators and from polarization fluctuations in fibres. The validation of our approach is achieved by the demonstration of the mode-locked laser frequency stabilization by optical injection leading to the reduction of the width of the injected mode by a factor greater than 1000, the transfer of the injection laser stability to all modes of the comb and the measurement of long term stability of the injected laser modes.
13th of December 2018 (Paris) - PhD defense of Grégoire Vallet: "Cavity assisted non destructive detection on a strontium optical lattice clock"

Grégoire VALLET will defend his thesis on 13th of December 2018 at 2:00 pm on the subject “Cavity assisted non destructive detection on a strontium optical lattice clock”, realized in SYRTE, under the supervision of Sébastien Bize and co-supervised by Jérôme Lodewyck.

The defense will take place in room 235A (2nd floor) at ENS, 29 rue d’Ulm 75005 Paris, in front of a jury composed of Caroline Champenois, Robin Kaiser, Jakob Reichel and Morgan Michell.

Abstract:

This thesis reports a high-performance Cs vapor cell atomic clock based on coherent population trapping (CPT).
This simple-architecture clock prototype combines a DFB diode laser (895 nm, Cs D1 line), a fibered electro-optical modulator driven by an ultra-low phase noise microwave frequency synthesizer, an acousto-optical modulator, a Michelson system, a buffer gas filled Cs vapor cell and FPGA-based low noise electronics.
The clock combines an optimized CPT pumping scheme, named push-pull optical pumping (PPOP), and a Ramsey-like pulsed interrogation, allowing the detection of high-contrast Ramsey-CPT fringes.
During this thesis has been implemented and adapted for this vapor-cell CPT clock, a novel interrogation protocol recently proposed by PTB for optical clocks, named Auto-Balanced Ramsey (ABR). This method, aiming to eliminate probe-induced frequency shifts, is based on the extraction of two error signals derived from two successive Ramsey sequences with different dark periods. The first feedback loop uses the error signal generated by the short Ramsey sequence to apply a phase-step correction to the local oscillator during the dark time that nulls the probe-field induced frequency shift. The second loop provides the means to stabilize the local oscillator frequency using the error signal derived from the long Ramsey sequence.
This ABR-CPT protocol, improved further with symmetrization (SABR-CPT), has allowed to reduce drastically the sensitivity of the clock frequency to laser power variations, by a factor 80 in comparison with a standard Ramsey-CPT interrogation. This CPT clock exhibits today the fractional frequency stability level of 2 10-13 τ-1/2, with best demonstrated mid-term stability at the level of 2.5 10-15 at 10 000 s.
Annex laser spectroscopy studies in Cs microfabricated cells were also performed in this thesis. We note the preliminary demonstration of a frequency-stabilized laser using dual-frequency sub-Doppler spectroscopy in a Cs microcell, exhibiting an encouraging fractional frequency stability lower than 2 10-12 at 1 s. These short-term stability performances are 10 times better than those of microwave CPT-based chip-scale atomic clocks.
12th of December 2018 (Besançon) - PhD defense of Grégoire Coget: "Coherent population trapping Cs cell atomic clock with Auto-Balanced Ramsey interrogation protocol"

Grégoire COGET will defend his thesis on 12th of December 2018 at 2:00 pm on the subject “Coherent population trapping Cs cell atomic clock with Auto-Balanced Ramsey interrogation protocol”, realized in FEMTO-ST Institute, under the supervision of Rodolphe Boudot.

The defense will take place at the Amphitheatre gagnepain of ENSMM, in front of a jury composed of Carlos Garrido Alzar, Martina Knoop, François Nez, François-Xavier Esnault, Rodolphe Boudot, Vincent Giordano.

Abstract:

This thesis reports a high-performance Cs vapor cell atomic clock based on coherent population trapping (CPT).
This simple-architecture clock prototype combines a DFB diode laser (895 nm, Cs D1 line), a fibered electro-optical modulator driven by an ultra-low phase noise microwave frequency synthesizer, an acousto-optical modulator, a Michelson system, a buffer gas filled Cs vapor cell and FPGA-based low noise electronics.
The clock combines an optimized CPT pumping scheme, named push-pull optical pumping (PPOP), and a Ramsey-like pulsed interrogation, allowing the detection of high-contrast Ramsey-CPT fringes.
During this thesis has been implemented and adapted for this vapor-cell CPT clock, a novel interrogation protocol recently proposed by PTB for optical clocks, named Auto-Balanced Ramsey (ABR). This method, aiming to eliminate probe-induced frequency shifts, is based on the extraction of two error signals derived from two successive Ramsey sequences with different dark periods. The first feedback loop uses the error signal generated by the short Ramsey sequence to apply a phase-step correction to the local oscillator during the dark time that nulls the probe-field induced frequency shift. The second loop provides the means to stabilize the local oscillator frequency using the error signal derived from the long Ramsey sequence.
This ABR-CPT protocol, improved further with symmetrization (SABR-CPT), has allowed to reduce drastically the sensitivity of the clock frequency to laser power variations, by a factor 80 in comparison with a standard Ramsey-CPT interrogation. This CPT clock exhibits today the fractional frequency stability level of 2 10-13 τ-1/2, with best demonstrated mid-term stability in quiet conditions at the level of 2.5 10-15 at 10 000 s.
Annex laser spectroscopy studies in Cs microfabricated cells were also performed in this thesis. We note the preliminary demonstration of a frequency-stabilized laser using dual-frequency sub-Doppler spectroscopy in a Cs microcell, exhibiting an encouraging fractional frequency stability lower than 2 10-12 at 1 s. These short-term stability performances are 10 times better than those of microwave CPT-based chip-scale atomic clocks.
12th of December 2018 (Besançon) - PhD defense of Jérémy Bon: "Résonateurs à ondes acoustiques de volume piégées à très basses températures : Application à l'optomécanique"

Jérémy BON will defend his thesis on 12th of December 2018 at 10:30 am on the subject “Résonateurs à ondes acoustiques de volume piégées à très basses températures : Application à l’optomécanique”, realized in FEMTO-ST Institute, under the supervision of Serge Galliou.

The defense will take plac eat the Amphitheatre Jules Haag of ENSMM, in front of a jury composed of Ludovic Bellon, Bernard Bonello, Pierre-François Cohadon, Gianpietro Cagnoli, Bernard Dulmet, Serge Galliou et Roger Bourquin.

Abstract:

For a few years, the Time and Frequency department in FEMTO-ST Insitute has been leading research about the behavior of Bulk Acoustic Wave (BAW) trapped in quartz crystal at cryogenic temperatures (near 4K).
The measured quality factor are around a few billions at few tens of MHz for such temperatures. Acoustical quartz cavities are therefore good candidates for ultrastable cryogenic frequency sources.
The work presented here is in the natural continuation of the research cited above. They aim at strenghtening the interest for quartz crystal, but also to consider alternative solutions with non-piezoelectric material with very-low acoustical losses, for which optical excitation is an option.
The following work can be summed up in three main parts:
– The first part is about the determination of a quartz crystal cut for which an turnover point exists in the frequency-temperature curve in the cryogenic region. Indeed, it is not enough to barely control the temperature in an ultrastable frequency source. Such an turnover point needs to be the operation point for thermal regulation. Searching a compensated cut arose the need for a preliminary measurements campaign of thermal coefficients of elastic coefficients of the material, which were unknown at low temperature.
It was then possible, based on these coefficients, to calculate and even realize a cut fulfilling the required condition.
– The second part had the objetive to demonstrate conceptually that using a quartz acoustical cavity as an optical cavity was feasable. In its basic scheme, a BAW quartz resonator is plano-convex (to ensure the trapping of the acoustic wave) and has electrodes (metal-made to ensure electrical excitation) deposited on each face. It has been demonstrated, both theoretically and experimentally, that such a geometry works fine as an optical cavity, with its corresponding advantages and limitations. This scheme is used for the optomechanical coupling discussed in the third part and constitutes the very base for more efficient optomechanical devices.
– The third part is dedicated to the evaluation of how efficient will such devices be while functioning at cryogenic temperature. A theoretical quantitication of the optomechanical coupling that these cavities might reach is also presented.
Producing an optomechanical cavity will allow avoiding the physical constraints imposed by the use of a cryogenerator and will open the way to the study of non-piezoelectric material with very low mechanical losses, similar or even lower than that of quartz.
This kind of experimentation also answers to the needs of other research teams working on quantum optomechanics or hybrid quantum systems (LKB, UWA, …) with which collaborations are currently being held.
11th of December 2018 (Besançon) - PhD defense of Etienne Vaillant: "Contribution à la mesure du bruit propre de résonateurs MEMS"

Etienne VAILLANT will defend his thesis on 11th of December 2018 on the subject “Contribution à la mesure du bruit propre de résonateurs MEMS”, realized in FEMTO-ST with Fabrice Sthal et Joël Imbaud.
3rd of December 2018 (Besançon) - PhD defense of Marianne Sagnard: "Design and development of surface elacstic wave components dedicated to passive and wireless sensors and to radiofrequency filtering"

Marianne SAGNARD will defend her thesis on 3rd of December 2018 at 2:00 pm on the subject “Design and development of surface elacstic wave components dedicated to passive and wireless sensors and to radiofrequency filtering”, realized in the context of a CIFRE DGA agreement in which frecnsys and FEMTO-ST were associated, under the supervision of Jean-Michel Friedt and Thierry Laroche.

The defense will take place at the Amphitheatre Jean-Jacques Gagnepain, Temis Sciences, 15 avenue des Montboucons, 25000 Besançon, in front of a jury composed of Victor Plessky, Anne-Christine Hladky, Yann Kersalé, Sami Hage Ali, Alexandre Reinhardt, Jean-Michel Friedt, Thierry Laroche.

The defense will be in french and will be followed by a buffet at ENSMM.

Abstract:

This thesis aims at designing innovative, passive and wireless surface acoustic waves (SAW) sensors and filters, dedicated to harsh environments. Several types of SAW components are consequently studied. The main characteristics, such as insertion losses or relative bandwidth, of usual structures (resonators, delay lines, LCRF, ladder filters…) are known by the experts. However, to design a SAW device that respects specific requirements, the definition of the proper behavior of each device must be established before the manufacturing. For this purpose, numerical models are developed. Not only they include the possibility to analyse he beha-vior of systems with complex geometry (ladder filters, apodised transducers) but they take into account disturbing phenomena (transverse modes, losses due to the intrinsic nature of the materials). The comparison between computations and measures points out the match between experimental results and calculations.
The implementation of these tools allows the development of innovative SAW sensors and filters thanks to a fast and reliable numerical analysis of their behavior. Thus, the design of resonators and sensors dedicated to a use at temperatures exceeding 700°C is studied. It is demonstrated that despite its inhomogeneity, Ba2TiSi2O8 is suitable for the manufacturing of SAW devices subject to high temperatures and in a frequency range from 300 MHz to the GHz. Furthermore, a structure composed of a three electrodes per wavelength transducer is used to produce re-sonators that are not subject to directivity effects when the temperature changes. This configuration offers the possibility to design sensors that use a single resonator (versus at least two until now). This last point makes smaller components possible and solves the question of a differential aging of the structures.
A second type of sensors, also passive and wireless, dedicated to humidity measurements, based on the use of a single SAW, is studied. In this new configuration, a LCRF is used as a transponder and the sensitive area is outsourced. The mode sensitivity (of more than a MHz) to the variation of a capacitance or a dipole antenna is numerically brought to light. In practice, the device manufacturing showed a differential variation of the resonances of several kHz depending on the electric condition applied to one of the ports.
This work highlights the ability to predict the behavior of SAW structures thanks to the development of dedicated software. Moreover, the analysis and the manufacturing of innovative sensors and filters pave the way to new functionalities.
15th of November 2018 (Meudon) - PhD defense of Hélène Pihan-Le Bars: "From atomic clocks to the MICROSCOPE mission: search for Lorentz invariance violations"

Hélène PIHAN-LE BARS will defend her thesis on 15th of November 2018 at 2:00 pm on the subject “From atomic clocks to the MICROSCOPE mission: search for Lorentz invariance violations”, realized in SYRTE under the direction of Peter Wolf and co-supervised by Christine Guerlin.

The defense will take place in the conference room of the building 9 (castle) of the site of Meudon of Paris observatory – 5, place Jules Janssen, 92190 Meudon -, in front of a jury composed of Eric Gourgoulhon, Saïda Guellati-Khélifa, Robertus Potting, Joël Bergé and Isabelle Petitbon.

The defense will be in french and will be followed by a buffet.
12th of November 2018 (Besançon) - PhD defense of Guillaume Wong: "Design of self-encapsulated surface acoustic wave sensors in intermediate frequencies into a prestressed environment"

Guillaume WONG will defend his thesis on 12th of November 2018 at 2:00 pm on the subject “Design of self-encapsulated surface acoustic wave sensors in intermediate frequencies into a prestressed environment”, realized in SYRTE under the direction of Bernard DULMET and Thomas BARON.

The defense will take place in the amphitheater J-J Gagnepain at TEMIS Sciences (Besançon).

Jury :
– M. CRUNTEANU STANESCU Aurelian – Chargé de Recherche CNRS, XLIM – Rapporteur
– M. AUBERT Thierry – Maître de Conférences HDR, Centrale-Supélec – Rapporteur
– M. THERON Didier – Directeur de Recherche CNRS, IEMN – Examinateur
– M. CHOLLET Franck – Professeur des Universités, Université de Franche-Comté – Examinateur
– M. DULMET Bernard – Professeur des Universités, E.N.S.M.M – Directeur de thèse
– M. BARON Thomas – Ingénieur de Recherche HDR, E.N.S.M.M – Codirecteur de thèse

The defense will followed by a buffet at Time and Frequency Department in ENSMM.

Abstract: This thesis is part of the research and development of surface elastic wave components for the harsh environments exceeding 600°C. The objective is the realization of surface elastic waves self-encapsulated components which can reach a temperature of 900 ° C. In this work, we introduce a modulization method allowing a finite element finite resolution of an inhomogeneous bias. This method allows to directly calculate the bias problem and to extract the parameters calculated with the perturbation method as well as other parameters. This method contributes to the improvement of the realism of numerical simulations of structures subjected to wide variations of environmental parameters. We describe in this manuscript the approach of the study, the design, the realization and the tests of unencapsulated surface wave resonators for air annealing cycles up to 900 ° C as well as a bench of measurements allowing to perform the measurements in situ. We also discuss the design and implementation of the encapsulation of these resonators by an innovative technology by Wafer-Level Packaging for high temperatures.
25th of June 2018 (Paris) - HDR defense of Sébastien BIZE: "Development and applications of microwave and optical atomic frequency standards"

Sébastien BIZE will defend his “habilitation à diriger des recherches” on 25th June 2018 at 11:00 am on the subject “Development and applications of microwave and optical atomic frequency standards”.

The defense will take place at Observatoire de Paris (77 av. Denfert-Rochereau, Paris 14ème) in room J-F Denisse.
20th of April 2018 (Paris) - PhD defense of Namneet KAUR: "Long range time transfer using optical fiber links and cross comparison with satellite based methods"

Namneet KAUR will defend her thesis on 20th of April 2018 at 2:00 pm on the subject “Long range time transfer using optical fiber links and cross comparison with satellite based methods”, realized in SYRTE under the direction of Philip Tuckey and the supervision of Paul-Eric Pottie. This thesis has been cofunded by FIRST-TF.

The defense will take place in the amphitheater of the Institut d’Astrophysique de Paris (IAP).

=> Abstract
27th of March 2018 (Paris) - PhD defense of François TRICOT: "Analysis and reduction of the frequency instability noise sources in a compact CPT clock"

François TRICOT will defend his thesis on 27th of March 2018 at 1:30 pm on the subject “Analysis and reduction of the frequency instability noise sources in a compact CPT clock”, realized in SYRTE under the direction of Stéphane Guérandel.

The defense will take place in the amphitheater of the Institut d’Astrophysique de Paris (IAP), in front of the jury: Agnès Maître, Frédéric Du Burck, Vincent Giordano, Virgile Hermann and Jean-Marc Lesage.

Abstract:

This thesis work has been granted by a CIFRE-Défense contract to study the frequency stabilities of an atomic clock based on coherent population trapping. The objective is to demonstrate a frequency stability in the range of 10^-13τ^-1/2 up to 10 000 s. A caesium vapour cell is used with a high-contrast excitation scheme using cross linear polarisations and a Ramsey interrogation. The short-term frequency stability is presented with the reduction of the phase and the laser power noise, both limiting clock performance at 1 s integration time. The optimisation of the microwave chain with a new local oscillator, and the implementation of a very low noise power lock loop have improved the frequency stability down to 2,3×10^-13 at 1 s integration time. The fluctuations analysis of the operating parameters (laser intensity, magnetic field, temperature, etc.) and the measurement of the clock frequency show that the medium-term frequency instability is mostly limited by laser power and magnetic field fluctuations at the level of 2×10^-14 at 2 000 s integration time. These analyses also show that laser power fluctuations, despite servo loop control, are related to polarisation fluctuations through temperature fluctuations inside the experiment isolation box. Finally, the studies of a dual-frequency and dual-polarisation laser for a compact CPT clock are presented, paving the way to industrialisation by reducing the optical bench.

Key words: atomic clock, vapour cell, coherent population trapping, Ramsey fringes, Dick effect, intensity noise, frequency stability.
21st of December 2017 (Paris) - PhD defense of Mehdi LANGLOIS: "Design and realisation of a cold atom gravity gradiometer"

Mehdi Langlois will defend his thesis on 21st of December at 3:00 pm on the subject “Design and realisation of a cold atom gravity gradiometer”, realized in SYRTE under the direction of Franck Pereira dos Santos and the supervision of Sébastien Merlet.

The defense will take place in the amphitheater of the Institut d’Astrophysique de Paris (IAP), in front of a jury composed of Christophe Daussy, Laurence Pruvost, Saïda Guellati-Khélifa, Philippe Bouyer and Bruno Desruelle. The entrance will be at 77 avenue Denfer-Rochereau, 75014 Paris.

Abstract:

This thesis is about the design and realisation of a new atomic interferometer experiment at SYRTE. It will allow ultra-sensitive measurements of the vertical gradient of gravity. This experiment will work using ultra-cold atoms as a source, prepared on an atom chip. It will use large momentum transfer beam-splitter, obtained by high order Bragg diffraction. The transport of atoms will be provided by moving optical lattices. A first part of the experimental setup was assembled and its operation was validated by producing a dual interferometer. This interferometer is performed on two atomic clouds produced successively from the same source of cold atoms, and interrogated by the same pair of Raman beams. A new method of differential phase extraction has been experimentally demonstrated. It is based on the exploitation of the correlations between the interferometer phase measurements and the estimation of the seismic phase provided by an additional classical sensor.
Keywords : atom interferometry, cold atoms, inertial sensor, gravimeter, gradiometer, atom chip.
12th of December 2017 (Paris) - HDR defense of Sylvain SCHWARTZ: "Nouvelles approches pour les mesures inertielles et l’information quantique avec de la lumière et des atomes"

Sylvain Schwartz will defend his “habilitation à diriger des recherches” on 12th December 2017 at 2:00 pm on the subject “Nouvelles approches pour les mesures inertielles et l’information quantique avec de la lumière et des atomes”.

The defense will take place at Ecole Normale Supérieure (24 rue Lhomond, Paris 5ème) in room L363/L365.

Abstract:

Since its inception at the beginning of the twentieth century, quantum physics has triggered many practical applications including semiconductors and lasers. In turn, some of these applications allowed physicists to gain more control on quantum systems, holding great prospects for a second generation of applications where the laws of quantum physics are harnessed at the elementary level. The research that I have been involved in at Thales then at Harvard University spans across some of these applications, namely laser gyroscopes, atomic sensors and quantum simulators. I will describe a new type of ring laser gyroscope that we have developed at Thales, based on a solid-state gain medium, with the aim to reduce the cost and increase the lifetime of these devices. I will also discuss some recent proposals of enhancing the performance of optical rotation sensors with slow and fast light. I will then move on to our project of atom-chip interferometry with thermal atoms, and discuss the potential applications in the field of acceleration measurements. Finally, I will describe the work that I have been doing at Harvard on a quantum simulator based on a defect-free chain of 51 neutral atoms interacting through their Rydberg states, which can be programmed and operated in a regime where classical simulations are no longer tractable. To conclude, I will present some future directions in the field of quantum technologies exploiting the synergies between these different projects.
12th of December 2017 (Paris) - PhD defense of Meropi MORFOULI: "From precision in time measurement to the theory of universal gravity (1630-1740)"

Meropi Morfouli will defend her thesis on 12th December 2017 at 2:30 pm on the subject “From precision in time measurement to the theory of universal gravity (1630-1740)”, realized at SYRTE laboratory under the direction of Christian Bracco and Efthymios Nicolaidis.

The defense will take place in Lecturing hall L 361, at ENS, 24 rue Lhomond, 75005 Paris.

Abstract:

Precision in time measurement is considered by historiography as an element that emerged simultaneously with the geometrization of natural phenomena. The scholars of the seventeenth century are therefore studied in this context as Natural Philosophers who consider as the only reliable argument the quantitative results of measurement and precision. In this thesis we have studied this emergence, in the emblematic framework of Newton’s gravitational theory. At first we defined the accuracy of time as an element that requires constant improvement through the instruments. We then divided the scientific knowledge into three distinct parts: the construction of the theory, its application and the confirmation of the theory. We studied the accuracy (here as synonyme of precision) in the measurement of time and its role as a validation element in all three parts with a focus on the former. In this framework of study we have shown that the thesis commonly used in historiography so far is problematic. Precision in the measurement of time has no direct causal relation with the geometrization of nature. Its importance in theories, on a case-by-case study, is evolutionary and has for a long time been confined to the technical aspects of knowledge before finding an important place in the theory. The study of technical aspects led us to explore documents related to the determination of longitudes at sea, and its intrinsic relationship to the development of trade between continents. In this context we have detailed previously unclear aspects of Galileo’s “time measurer”, proposed by the later as an instrument of great accuracy being part of the longitude solution.
24th of November 2017 (Paris) - PhD defense of Denis SAVOIE: "Continuous and interleaved operation of a cold atom gyroscope and improvement of its stability"

Denis Savoie will defend his thesis on 24th November 2017 at 2 pm on the subject “Continuous and interleaved operation of a cold atom gyroscope and improvement of its stability”, realized at SYRTE laboratory under the direction of Arnaud Landragin and co-supervised by Remi Geiger.

The defense will take place in the main amphitheater of the Institut d’Astrophysique de Paris.
21st of November 2017 (Paris) - PhD defense of Romain BOUCHAND: "Optical frequency comb-based ultralow phase noise photonic microwave generation"

Romain Bouchand will defend his thesis on 21st November 2017 at 4 pm on the subject “Optical frequency comb-based ultralow phase noise photonic microwave generation”, realized at SYRTE laboratory under the direction of Yann Lecoq.

The defense will take place in the main amphitheater of the Institut d’Astrophysique de Paris.

The defense will be in english.

Abstract:

State-of-the-art microwave oscillators are typically bulky systems requiring tedious maintenance which is hindering their use in mobile applications or in demanding environments. The invention of the optical frequency combs, which was awarded a Nobel prize 2005, was a game- changer as it enabled a high-ﬁdelity tranfsfer of the unrivalled properties of optical oscillators to the microwave domain. In the technique used at SYRTE, the optical frequency division, a microwave signal can be extracted from a near-infrared ultra-stable laser using photodetection. The transfer is accompanied by a reduction of phase noise equal to the microwave-to-optical frequency ratio squared, I.E. more than eight order of magnitudes. This beneﬁt is however reduced by several processes producing excess noise during the transfer. The work described in this thesis is the generation of the lowest phase noise microwave signal ever reported. The diﬀerent processes inducing excess noise are analysed and, in part, overcome. Speciﬁcally, the conversion of the femtosecond laser intensity noise to the microwave phase noise is studied thoroughly and its eﬀect signiﬁcantly reduced. The results augur that the optical approaches in microwave generation are on the verge to disrupt the state-of-the-art. The noise level demonstrated and the techniques developed can beneﬁt a large range of domains such as mobile radars, time and frequency metrology or the next generation of ultrafast telecommunication networks.

Keywords : microwave photonics, ultra-stable lasers, optical frequency combs, low-noise oscillators
10th of November 2017 (Paris) - PhD defense of Slawomir BILICKI: "Strontium optical lattice clocks: clock comparisons for timescales and fundamental physics applications"

Slawomir Bilicki will defend his thesis on 10th November 2017 at 2 pm on the subject “Strontium optical lattice clocks: clock comparisons for timescales and fundamental physics applications”, realized at SYRTE laboratory under direction of Sébastien Bize and supervised by Jérôme Lodewyck.

The defense will take place in the main amphitheater of the Institut d’Astrophysique de Paris.

The defense will be in english.

Abstract:

This thesis describes the latest progresses regarding the Sr optical lattice clocks at LNE-SYRTE, Observatoire de Paris. Nowadays, the systematic uncertainty and stability of optical clocks are 2 orders of magnitude better than cesium microwave fountains currently realizing the SI second, with applications in fundamental physics, astronomy and geoscience. In the near future, a re-deﬁnition of the SI second is expected, once optical clocks are proven to be as reliable and reproducible as their microwave counterparts. The thesis presents three decisive steps in this direction. First, we demonstrate nearly con- tinuous Sr clocks over several weeks. Second, local and remote frequency comparisons against various microwave and optical frequency standards show that OLCs are reproducible over time, and by independent laboratories. We notably demonstrated the ﬁrst all-optical agreement between optical clocks at continental scale. Third, the Sr clocks were used to calibrate the Temps Atomique International (TAI). The ﬁve calibration reports, which we produced, were validated by the BIPM, as the ﬁrst contribution to TAI with optical clocks. In addition, some of these results were used to improve bounds on a putative violation of the Lorentz invariance by testing the stability of the frequency ratio between remote clocks. Finally, we conducted a full characterization of the frequency shifts associated with semi-conductor laser sources for the trapping light, including optical measurements and frequency shifts measurements, with applications for transportable and space clocks.
26th of October 2017 (Paris) - PhD defense of Hélène FLEURBAEY: "Frequency metrology of the 1S-3S transition of hydrogen: contribution to the proton charge radius puzzle"

Hélène Fleurbaey will defend her thesis on 26th October 2017 at 2 pm on the subject “Frequency metrology of the 1S-3S transition of hydrogen: contribution to the proton charge radius puzzle”, realized at Laboratoire Kastler Brossel under the supervision of François Nez.

The defense will take place in the Durand amphitheater at the Jussieu campus of Université Pierre et Marie Curie (4 place Jussieu, 75005 Paris).

The defense will be in english.

Abstract:

The precise measurement of the 1S-3S transition frequency of hydrogen could have a great impact on the proton charge radius puzzle, which results from the recent spectroscopy of muonic hydrogen. In our experiment, the two-photon 1S-3S transition is excited in a hydrogen atomic beam, with a continuous-wave 205-nm laser which is obtained by sum frequency generation in a non-linear crystal. The transition frequency is measured with respect to the LNE-SYRTE Cs clock by means of a frequency comb.
Recording the signal for several values of an applied magnetic field allows to estimate the velocity distribution of the atoms in the beam and deduce the second-order Doppler shift. Other frequency-shifting systematic effects have been taken into account: cross-damping, light shift, collisions. A complete study has shown that the velocity distribution does not depend significantly on the pressure, and allowed to determine the collisional shift.
Eventually, a value of the 1S-3S transition frequency is obtained with an uncertainty of about 5 kHz, or a relative uncertainty of 1.7 10^-12.
It is in very good agreement with the CODATA recommended value. This new measurement contributes to the ongoing search to solve the proton radius puzzle.
20th of October 2017 (Torino, Italy) - PhD defense of Carolina CARDENAS: "Digital Instrumentation for the Measurement of High Spectral Purity Signals"

Carolina Cárdenas will defend her thesis on 20th october 2017 on the subject “Digital Instrumentation for the Measurement of High Spectral Purity Signals”, realized at FEMTO-ST Institute under the supervision of Enrico Rubiola.

The defense will take place at Politecnico di Torino (Torino, Italy).

The defense will be in english.

Abstract:

Improvements on electronic technology in recent years have allowed the application of digital techniques in time and frequency metrology where low noise and high accuracy are required, yielding flexibility in systems implementation and setup. This results in measurement systems with extended capabilities, additional functionalities and ease of use.
The Analog to Digital Converters (ADCs) and Digital to Analog Converters (DACs), as the system front- end, set the ultimate performance of the system in terms of noise. The noise characterization of these components will allow performing punctual considerations on the study of the implementation feasibility of new techniques and for the selection of proper components according to the application requirements. Moreover, most commercial platforms based on FPGA are clocked by quartz oscillators whose accuracy and frequency stability are not suitable for many time and frequency applications. In this case, it is possible to take advantage of the internal Phase Locked Loop (PLL) for generating the internal clock from an external frequency reference. However, the PLL phase noise could degrade the oscillator stability thereby limiting the entire system performance becoming a critical component for digital instrumentation. The information available currently in literature, describes in depth the features of these devices at frequency offsets far from the carrier. However, the information close to the carrier is a more important concern for time and frequency applications.
In this frame, my PhD work is focused on understanding the limitations of the critical blocks of digital instrumentation for time and frequency metrology. The aim is to characterize the noise introduced by these blocks and in this manner to be able to predict their effects on a specific application. This is done by modeling the noise introduced by each component and by describing them in terms of general and technical parameters. The parameters of the models are identified and extracted through the corresponding method proposed accordingly to the component operation. This work was validated by characterizing a commercially available platform, Red Pitaya. This platform is an open source embedded system whose resolution and speed (14 bit, 125 MSps) are reasonably close to the state of the art of ADCs and DACs (16 bit, 350 MSps or 14 bit, 1 GSps/3GSPs) and it is potentially sufficient for the implementation of a complete instrument. The characterization results lead to the noise limitations of the platform and give a guideline for instrumentation design techniques.
Based on the results obtained from the noise characterization, the implementation of a digital instrument for frequency transfer using fiber link was performed on the Red Pitaya platform. In this project, a digital implementation for the detection and compensation of the phase noise induced by the fiber is proposed. The beat note, representing the fiber length variations, is acquired directly with a high speed ADC followed by a fully digital phase detector. Based on the characterization results, it was expected a limitation in the phase noise measurement given by the PLL. First measurements of this implementation were performed using the 150 km-long buried fibers, placed in the same cables between INRiM and the Laboratoire Souterrain de Modane (LSM) on the Italy-France border. The two fibers are joined together at LSM to obtain a 300 km loop with both ends at INRiM. From these results the noise introduced by the digital system was verified in agreement with characterization results. Further test and improvements will be performed for having a finished system which is intended to be used on the Italian Link for Frequency and Time from Turin to Florence that is 642-km long and to its extension in the rest of Italy that is foreseen in the next future.
Currently, a higher performance platform is under assessment by applying the tools and concepts developed along the PhD. The purpose of this project is the implementation of a state of the art phasemeter whose architecture is based on the DAC. In order to estimate the ultimate performance of the instrument, the DAC characterization is under development and preliminary measurements are also reported here.
11th of October 2017 (Paris) - PhD defense of Maxime FAVIER : "Mercury optical lattice clock: from high-resolution spectroscopy to frequency ratio measurements"

Maxime Favier will defend his thesis on 11th october 2017 at IAP (Paris) at 14:00 on the subject “Mercury optical lattice clock: from high-resolution spectroscopy to frequency ratio measurements”, realized at the SYRTE under the direction of Sébastien Bize and supervised by Sébastien Bize and Luigi De Sarlo.

The defense will take place in room “Salle des séminaires” of the “Institut d’Astrophysique de Paris” (IAP) located 98 bis boulevard Arago, 75014 Paris, in front of a jury composed of Martina Knoop, Leonardo Fallani, Thomas Udem, Philippe Grangier and Jean-Michel Raimond.

The defense will be in english.

Abstract:
This thesis presents the development of a high-accuracy optical frequency standard based on neutral mercury 199Hg trapped in an optical lattice. We will present the experimental setup and the improvements that were made during this thesis, which have allowed us to perform spectroscopy on the doubly forbidden 1S0 -> 3P0 mercury clock transition at the Hz level resolution. With such a resolution, we have been able to perform an in-depth study of the physical effects affecting the clock transition. This study represents a factor 60 improvement in accuracy on the knowledge of the clock transition frequency, pushing the accuracy below the current realization of the SI second by the best cesium atomic fountains. Finally, we will present the results of several comparison campaigns between the mercury clock and other state-of-the-art frequency standards, both in the optical and in the microwave domain.
4th of October 2017 (Paris) - PhD defense of Theo LAUDAT: "Spontaneous spin squeezing in a spinor Bose-Einstein condensate trapped on an atom chip"

Théo Laudat will defend his thesis on 4th october 2017 at IAP (Paris) at 2 pm on the subject “Spontaneous spin squeezing in a spinor Bose-Einstein condensate trapped on an atom chip”. This work has been done in SYRTE under the supervision of Noel Dimarcq, Peter Rosenbusch, Carlos Garrido Alzar and Jakob Reichel.

The defense will be in english.

Abstract:
In this manuscript, we present an experimental study of spin squeezing in a spinor Bose-Einstein condensate of 87Rb, arising from a non-linear interaction originating from collisions between the two internal states |F = 1,mF = −1 > and |F = 2,mF = 1 > of the 52S1/2 manifold. The atoms are cooled down in a magneto-optical trap and magnetically trapped thanks to our atom-chip which acts as a top wall for our vacuum cell. The chip is also used to emit the radio-frequency field that perform the evaporative cooling leading to Bose-Einstein condensation, and the microwave field used to coherently transfer the atoms from one internal state to another. The atomic ensemble in a coherent superposition is well described by the so-called textitone-axis-twisting Hamiltonian that contains a term quadratic in the z-component of the spin vector Sz. the strength of this non-linear interaction, initially very weak, depends on the intra- and inter-state s-wave scattering lengths, and can be greatly enhanced by reducing the wave-function spatial overlap between the two states. We therefore place the system in a configuration (high atom number and cigar-shaped trap) for which the two states experience spontaneous relative spatial separation and recombination phases. The impact of this spatial dynamics on the mean field interaction and coherence of the system is experimentally analyzed through the study of the contrast and central frequency of a Ramsey interferometer. Theoretically, when the two states are separated, the spin noise distribution evolves from a uniform circular distribution defined by the quantum projection noise, to an elliptic one whose small axis is smaller than the standard quantum limit, under the action of the S2 z interaction. This is verified experimentally by performing the tomography of the atomic state, when the two internal modes recombine. A squeezing parameter xi2 = −1.3pm0.4 dB is reached for 5000 atoms and a 90% contrast. The study of the different instability sources highlights the atomic-density-dependent losses as the main limitation for both the noise reduction and the contrast of the interferometer. This work has been initiated in the context of quantum metrology and represents a step towards the production of spin squeezed states enabling the realization of atom interferometers working below the standard quantum limit. It also addresses the fundamental question of coherence of spinor Bose-Einstein condensates undergoing many elastic and inelastic collisions.
21st of September 2017 (Paris) - PhD defense of Charles PHILIPPE: "Source laser à 1.5 µm stabilisée en fréquence sur l'iode moléculaire"

Charles PHILIPPE will defend his PhD on the 21st of September, 2017 at IAP (Paris) on the topic “Source laser à 1.5 µm stabilisée en fréquence sur l’iode moléculaire”.

This work took place at SYRTE laboratory under the supervision of Ouali ACEF and Peter WOLF.

Abstract:

This thesis reports on the development of a frequency stabilization of a 1.54 µm laser diode on iodine hyperfine line at 514 nm, after a frequency tripling process.

An important part of this work is dedicated to the development of the frequency tripling process of a 1.54 µm laser diode, using two periodically polled wave guided Lithium Niobate nonlinear crystals. A nonlinear conversion efficiency P₃_w/P_w > 36 % is obtained. This result is the best efficiency ever demonstrated for a CW frequency tripling process. 300 mW of harmonic power is generated at 514 nm from a fundamental optical power of 800 mW at 1.54 µm. The optical setup is fully fibered. The total power consumption needed to fulfill this frequency tripling process is 20 W only. According a specific operation mode, this laser setup emits simultaneously three frequency-stabilized and intense radiations at 1.54 µm, 771 nm and 514 nm.

Following this development, a very compact laser spectroscopy setup is buildup, based on a short sealed quartz cell, which contains the molecular iodine vapor. An optical power lower than 10 mW in the green is sufficient to fulfill the iodine vapor interrogation, and to detect the hyperfine saturation transitions, whose have a high factor around 514 nm (Q > 2×10⁹).

A frequency stability at the level of 4.5 x 10^-14 t^-1/2with a minimum value of 6 x 10^-15from 50 s to 100 s is demonstrated in this study. This frequency stability is the best result ever conferred to a laser diode at 1.54 µm, using in simple way a Doppler-free iodine spectroscopy technique.

This work has allowed to identify the major key components, in order to develop in near future, a fully fibered and compact stabilized laser prototype occupying a total optical volume < 10 liters.

This development could answer to numerous needs of space mission’s projects requiring ultra-stable frequency optical link, inter-satellite or ground to space, for the space geodesy (GRICE), the earth gravitational field measurement (GRACE-FO, NGGM), the gravitational waves detection (LISA) , etc …

Keywords: Metrology, frequency stabilization, ultra-stable lasers, Iodine optical clock, nonlinear optic, tripling frequency process, Telecom Laser, 1.5 µm, 514 nm, space.
5 septembre 2017 (Le Mans) - Soutenance de thèse de Paulo DE OLIVEIRA: "Définition et Mise en Oeuvre d’un Nouveau Service de Positionnement Précis par GNSS"

Soutenance de thèse de Paulo de Oliveira, doctorant CIFRE de l’entreprise Geodata Diffusion (Hexagon Geosystems), du laboratoire GeF (Géomatique & Foncier) et du PPGCC (Programa de Pós-graduação em Ciências Cartográficas), présentera ses travaux de recherche en vue de l’obtention du titre de docteur du Cnam (Conservatoire National des Arts et Métiers) et de Unesp (l’Université de Sao Paulo), à l’occasion d’une soutenance publique qui aura lieu le :
05 septembre 2017 à 14 heures, à l’Université du Mans (maison de l’université, salle des conseils), sur le sujet :
Définition et Mise en OEuvre d’un Nouveau Service de Positionnement Précis par GNSS

=> Résumé des travaux
30th of June, 2017 (Palaiseau) - PhD defense of Nicolas Von Bandel : "Development and study of low noise laser diodes emitting at 894 nm for compact cesium atomic clocks"

Nicolas VON BANDEL will defense his thesis the 30th of June, 2017 at III-V Lab (Palaiseau) on the subject “Development and study of low noise laser diodes emitting at 894 nm for compact cesium atomic clocks”. This work was a collaboration between Institut d’Electronique et des Systèmes (Montpellier) and III-V Lab (Palaiseau).

Abstract :

This PhD work deals with the design, the fabrication and the study of high-coherence semiconductor laser sources emitting at 894 nm, for application to compact, optically-pumped cesium atomic clocks in an industrial context. We are particularly interested in the electrically pumped ”Distributed-Feedback” in-plane laser diodes (DFB). The aim is to obtain a low-threshold, single-mode laser with high optical efficiency and a linewidth of less than 1 MHz. We first deal with the design and first-order characterization of the DFB diodes until they are put into modules for the clock. We then carry out an in-depth study of the physical properties of the laser emission in terms of coherence time. For that purpose, a new universal method for characterizing the optical frequency noise is introduced. Finally, we look further into the spectral properties of the emission in a servo configuration on a fluorescence line of the cesium (”Dither-Locking”). We show that the intrinsic properties of the component satisfy the requirements of the industrial system as defined in the study.
1^st June 2017 (Besançon) - Thesis defense of Moustafa Abdel Hafiz: "Development and metrological characterization of a high-performance Cs cell atomic clock based on coherent population trapping"

Moustafa ABDEL HAFIZ will defend his thesis on Juine, 1st, 2017 at ENSMM (Besançon) on the subject “Development and metrological characterization of a high-performance Cs cell atomic clock based on coherent population trapping”.

This work has been realized at FEMTO-ST laboratory under the supervision of Rodolphe BOUDOT and Vincent GIORDANO. This thesis has been co-funded by FIRST-TF.

Résumé :

Ce travail de thèse, financé par le LabeX FIRST-TF et la Région de Franche-Comté, effectuée dans le cadre du projet européen MClocks (http://www.inrim.it/mclocks), reporte le développement et la caractérisation métrologique d’une horloge atomique à cellule de césium de haute performance basée sur le phénomène de piégeage cohérent de population (CPT). Cette horloge atomique, avec un fort potentiel de compacité et à vocation future industrielle, pourrait trouver à terme des applications pour les systèmes de télécommunications, d’instrumentation, de défense ou navigation par satellite.
8 December 2016 (Palaiseau) - Thesis defense of Paul Dumont : "Dual-frequency optically-pumped semiconductor laser for atomic clocks based on coherent population trapping of cesium atoms"

Paul Dumont will defend his thesis on Dec. 8th, 2016 at 13:30, Institut d’Oprique (Palaiseau) on the subject “Dual-frequency optically-pumped semiconductor laser for atomic clocks based on coherent population trapping of cesium atoms”. This work has been realized at LCF – Laboratoire Charles Fabry under the supervision of Gaelle Lucas-Leclin and Patrick Georges. This thesis has been co-funded by FIRST-TF.

Abstract :

Atomic clocks using the coherent population trapping (CPT) technic are excellent candidates to obtain frequency references that are stable, compact and with a low power consumption. In the case of cesium atomic clocks, this technic require a dual-frequency laser eld either at 895 nm (D1 transition) or 852 nm (D2 transition) and whose frequency diference is equal to 9.19 GHz, the frequency splitting between the two hyperne levels of the fundamental state. Here we present a new concept for generating this type of laser eld using a unique dual frequency and optically-pumped laser with a dual-polarized emission. In this manuscript, we study the conception of such a laser source with an emission tunable at the D2 transition of cesium atoms. We detail the design of the intracavity elements and the semiconductor active structure. Then we describe the experimental set-up and characterization of a rst prototype. We present the stabilization set-up of the laser based on two diferent servo-loops, one used to lock the frequency onto the cesium transition and the other to lock the frequency dierence onto the frequency generated by a local oscillator. We report a complete simulation and characterization of the main laser noises: the laser intensity noise, the optical frequency noise, and the phase noise of the radiofrequency signal generated by the beatnote of the two laser modes. We show the rst experimental results of coherent population trapping obtained with the prototype. Finally we establish a noise budget of a CPT atomic clock by estimating the impact of each laser noises. After we identify the system limits, we propose dierent ways to improve the dual-frequency which rely on the reduction of the intensity noise and the modication of the semiconductor structure design.
2 Décembre 2016 (Toulouse) - Soutenance HDR de Félix Perosanz : "La contribution des systèmes de navigation par satellites aux géosciences"

Félix Perosanz soutiendra son Habilitation à Diriger des Recherches le 2 décembre 2016 à 13h30 salle Coriolis, Observatoire Midi Pyrénées, 14 av. Edouard Belin à Toulouse.

Sur le sujet ” La contribution des systèmes de navigation par satellites aux géosciences”.

Résumé : Si les systèmes de navigation par satellite comme le GPS ont intégré notre quotidien, ils ont aussi bouleversé le monde des géosciences et celui de la géodésie en particulier. Cette science qui a pour objet de réaliser des systèmes de référence et de mesurer la forme, les déformations et l’orientation de la Terre, joue un rôle fondamental dans l’appréhension du système Terre et de son évolution. L’exposé fera la synthèse de mes 20 années de recherche consacrées au traitement géodésique de données GNSS avec le logiciel GINS du CNES/GRGS. J’exposerai notamment pourquoi l’idée que notre équipe devienne « Centre d’Analyse » de « l’International GNSS Service » s’est imposée et comment j’ai œuvré (en partenariat avec la société CLS) pour que cela devienne une réalité. Les traitements qui sont réalisés en routine depuis 2010 pour le compte de ce service ont la spécificité de produire des solutions d’orbite/horloge des satellites conservant la « propriété entière » des mesures de phase GPS. L’utilisation de ces produits donne ainsi accès au mode de « Positionnement Ponctuel Précis » avec fixation des ambiguïtés de phase (IPPP) qui s’impose aujourd’hui comme une alternative au mode classique différentiel (qui a l’inconvénient de nécessiter des stations de référence). L’intérêt d’un nombre croissant de laboratoires pour ce mode de positionnement IPPP avec nos logiciels et produits a été à l’origine de nombreuses coopérations scientifiques et de co-encadrement d’étudiants. Mon exposé sera illustré par des résultats issus d’études variées sur la déformation de glaciers, le niveau des océans, la réalisation de « profils en long » de fleuves, la propagation d’ondes sismique ou encore le transfert de fréquence entre horloges atomiques. J’aborderai enfin les principaux thèmes de prospective de mes futures activités dont l’objectif est de poursuivre l’amélioration des traitements GNSS au service des géosciences en incluant notamment les données du système Européen Galileo.

Le jury sera composé de :

Olivier Vanderhaeghe, GET/UPS (Président)

Zuheir Altamimi, IPGP/LAREG (Rapporteur)

Pierre Briole, ENS Paris (Rapporteur)

Pierre Exertier, OCA/Géoazur (Rapporteur)

Andrea Walpersdorf, ISTerre (Examinatrice)

Richard Biancale, GET/CNES (Tuteur)
30 november 2016 (Paris) - Seminar of Frank Quinlan (NIST, USA) : "Optical to RF frequency generation with optical frequency combs"

Seminar of Labotory Kastler Brossel, will be held on Wednesday November 30 at 13:45 in room 2 of the Collège de France, Paris

The most frequency-stable electromagnetic radiation is now produced optically, with stable reference cavities demonstrating fractional frequency instabilities below 10^-16 at 1 second and optical clocks reaching 10^-18 at 10^4 seconds. This talk will cover recent work at NIST using optical frequency combs to transfer this stability across the optical domain at the level of 10^-18 at 1 second, as well as into the RF, microwave, and mm-wave domains at the level of 10^-15 to 10^-17 at 1 second. In addition to the optical frequency combs themselves, elements of compact ultrastable optical cavities, high-speed photodetection and broadband electronic synthesis will also be discussed.
29 november 2016 (Besançon) - Thesis defense of Nikolay Vorobiev"Miniaturization of OCXO oscillators for space applications"

Defense realized at FEMTO-ST, which will be partly public, will take place on Tuesday, 29 of november 2016 at 14:00 in Amphithéatre Mesnage, ENSMM, 26 rue de l’Epitaphe, Besançon.

This thesis presents the work on designing a miniature temperature controlled crystal oscillator (required volume is 1 cm3). TTC (Telemetry, Tracking and Control) equipment which is used in microsatellites (as Myriades) has a very important volume (8 liters). 8 times lower volume equipment (1 liter) is planned for pico and nano satellites. Therefore, a significant reduction of volume and consumption for equal performance is necessary. Redesign is required for all components of equip-ment items including micro-oscillator, as in volume as at the level of energy consumption. Preliminary studies have served to define the resonator adapted to satisfy the request stability specifications. Thermal simulation of an OCXO oscillator model (Oven Con-trolled Xtal Oscillator) has permitted to achieve a good understanding of heat transfer into the device. Reducing heat loss and increases the thermal stability of resonator were major challenges. Thermal expansion of the resonator causes mechanical stresses in its mountings and shifts the resonance frequency. A silicon MEMS has designed for supporting the resonator by using thermomechanical simulations. This support is compatible with the constraints of low consumption and heat sensitivity retaining good impact resistance. As regards electronics, an ASIC chip which is used during many years has characterized with the purpose to obtain the digital model. This study has revealed the limiting factors of the oscillator performance. Also it has allowed to provide remedial solutions. The ASIC using was rejected in favor of the solution operating with commercial electronic components (at least temporarily). Finally, a miniature demonstrator of physical module was assembled and characterized. The measuring results show that demonstrator consumption remains below the required specification. The importance of the participation of radiation within the thermal exchanges has also validated experimentally.

Keywords: acoustic resonator, quartz, OCXO oscillator, phase noise, thermal control, force-frequency effect, thermomechanical modeling, miniaturization.
18 november 2016 (Paris) - Thesis defense of Satyanarayana BADE : "Propagation of atoms in a magnetic waveguide on a chip"

Defense on Thursday, 18 of november 2016 at 14:00 in Room “Salle des séminaires” of the “Institut d’Astrophysique de Paris” (IAP).

This entrance will take place : 77 avenue Denfert Rochereau – 75014 Paris

The Thesis will be in english
In this thesis we study the propagation of atoms in a magnetic toroidalwaveguide, with the aim of developing an inertial sensor. Here, we present differentstrategies to create the waveguide on an atom chip for a guided Sagnac atominterferometer. We devised three solutions which can be achieved using the samewire configuration. They use the current modulation technique, from a new pointof view, which simultaneously tackles the problem of wire corrugation and spindependent Majorana atom losses. The effect of the multimode propagation of theatoms in the guide is also quantified in this thesis. Using a simple model, we coveredthe propagation of noninteracting ultracold and thermal gases. We identifiedthe operating conditions to realize a cold atom interferometer with a large dynamicrange essential for applications in inertial navigation. Experimentally, the thesisdescribes the realisation and characterisation of the cold atom source close to agold coated substrate, as well as the implementation and the characterisation of theatom detection systems.
4 november 2016 (Paris) - Thesis defense of Pierre Gillot : "Long term stability of a cold atom gravimeter and limit of the rejection technic of systematics effects"

Defense on Thursday, 4 of november 2016 at 14:00 in Room “Salle des séminaires” of the “Institut d’Astrophysique de Paris” (IAP).

This entrance will take place : 77 avenue Denfert Rochereau – 75014 Paris

Work installed at the LNE at Trappe under the supervision Franck Pereira Dos Santos and Sébastien Merlet

This thesis aims at pushing the performances of the atom gravimeter CAG developed at SYRTE. This instrument uses atom interferometry to measure the local gravity acceleration of a free falling 87Rb cold atomic cloud. The improvements of the Raman power control and parameters such as those driving the detection are presented in this thesis. The initial position of the cloud, its mean velocity, its ballistic expansion into the Raman beams and thus their evolution, are important parameters which affect the performances of the CAG. The resulting coupling inhomogeneities modify the symmetry of the sensitivity function of the interferometer and make it sensitive to constant Raman detuning. Moreover, the Raman detuning in a Doppler way cannot be canceled by our rejection technic of systematic effects. The asymmetry of the sensitivity function has been measured and a method is demonstrated to cancel it. Several comparisons between the CAG and different gravimeter types have been performed and their results are developed. The international comparison of absolute gravimeters CCM.G-K2 confirms the CAG accuracy budget. It reveals an Allan standard deviation of 5.710-9g/Hz1/2. In the end, a one month common view measurement with a superconducting gravimeter iGrav is studied. The determination of the iGrav scale factor at the level of 0.1% in a single day and 0.02% in less than a month is obtained with this long measurement. The Allan standard deviation of the gravity residual signal is 610-11g in 12h measurement time.
3 november 2016 (Paris) - Thesis defense of Cyrille SOLARO "TRAPPED ATOM INTERFEROMETERS : FROM LOW TO HIGH DENSITY REGIME"

Defense on Thursday, 3 of november 2016 at 14:00 in Room “Salle des séminaires” of the “Institut d’Astrophysique de Paris” (IAP).

This entrance will take place : 77 avenue Denfert Rochereau – 75014 Paris

The Defense will be made in french.
Work realized at the SYRTE under the supervision Franck Pereira Dos Santos

This thesis presents the recent progress on the FORCA-G (FORce de CAsimir et Gravitation à courte distance) experiment which aims at measuring short range forces between an atom, trapped in a vertical optical lattice, and a mirror. Stimulated Raman transitions are used to induce coherent transport between adjacent lattice sites to perform atom interferometry in order to measure with very high sensitivity, shifts in the Bloch frequency ÜB, which is the potential increment between two lattice sites. For low atomic densities, we demonstrate a local force sensor with state-of-the art relative sensitivity on the Bloch frequency of 1.8 × 10−6 at 1 s. The recent use of evaporative cooling, in order to increase the number of atoms per well, allows to work the experiment with much denser atomic clouds where atom interactions cannot be neglected. At densities of 10^11 − 10^12 at/cm3, it is shown that a spin self-rephasing mechanism competes with the spin-echo technique. The impact of the former mechanism onto the contrast and the measured frequency is studied in an interferometer where the two partial wave packets perfectly overlap. First measurements are then performed in a regime where the two partial wave packets are spatially separated. They show a different behavior that remains to be modelled.

Finally, it is shown that the measurement protocol allows to greatly reduce collisional shifts:
atom interactions limit the sensitivity of the local force sensor without limiting its accuracy.
Key-words : atom interferometry, short-range forces, ultracold atoms, inertial sensor, optical lattice, spin self-rephasing
7 Octobre 2016 (Paris) - Thesis defense of Clément COURVOISIER "Condensat de Bose-Einstein par refroidissement évaporatif dans un piège dipolaire pour la métrologie par interférométrie atomique"

Defense on Friday, 7 of October 2016 at 14:00 at UPMC – 4 Place Jussieu – 75005 Paris

This research work fulfilled as part of my PhD project involved to design, build and characterise a new experimental setup based on an atom source by evaporative cooling in an optical dipole trap. It goes after the improvement of the uncertainty on the measurement of the ratio h/m between Planck’s constant and the rubidium atom mass, reducing the Gouy phase and wavefront curvature.
In a first step we have studied several optical configurations to optimise the dipole trap loading: the 50 W beam at 1070 nm is shaped in a double 93 μm waist reservoir and one crossed 20 μm waist dimple. After having optimised and caracterised the evaporative process, we obtained one Bose-Einstein condensate.
Furthermore, for Raman interferometry, we set up a new laser system at 1560 nm based on frequency doubling. We developed a double cervo loop: on the one hand, it allows to phase lock the two laser sources, and on the other hand to correct phase noise accumulated in fibered amplifiers.
Today, our new experimental setup is ready to perform atom interferometry on a Bose-Einstein condensate.
30 september 2016 (Paris) - Thesis defense of Konstantin OTT : "Towards a squeezing-enhanced atomic clock on a chip"
Defense on Friday, 30 of September 2016 at 14:00 – in Room “Salle des séminaires” of the “Institut d’Astrophysique de Paris” (IAP) – 98 bis Boulevard Arago – 75014 Paris

Work realized at the SYRTE and the Laboratoire Kastler Brossel under the supervision Peter ROSENBUSCH and Jakob REICHEL

In front of a jury composed of Philippe Bouyer – Matthias Keller – Agnès Maitre – François-Xavier Esnault – Tilo Steinmetz et Jean-Marc Lasage
```
This defense will be in english.
```
This thesis describes the conception and construction of an “entanglement-enhanced”

trapped atom clock on an atom chip (TACC). The key feature of this new experiment

is the integration of two optical Fabry-Pérot micro resonators which enable generation

of spin-squeezed states of the atomic ensemble via atom-light interactions and non-

destructive detection of the atomic state.

It has been shown before that spin-squeezed states can enhance the metrological

performance of atomic clocks, but existing proof-of-principle experiments have not yet

reached a metrologically relevant level of precision. This is the ﬁrst goal of the new

setup.

To retain the compactness and stability of our setup, we chose the optical resonator

to be a ﬁber Fabry-Pérot (FFP) resonator where the resonator mirrors are realized on

the tip of optical ﬁbers. To meet the requirements of our experiment, a new generation

of FFP resonators was developed in the context of this thesis, demonstrating the longest

FFP resonators to date. For this purpose, we developed a “dot milling” procedure using

a focused CO2-laser that allows shaping of fused silica surfaces with unprecedented

precision and versatility. Beyond the TACC experiment these long FFP resonators

open up new applications in other fields as in the ion trapping community or for

frequency filtering.

Incorporating optical resonators in the TACC system necessitates a new atom chip

design, allowing transportation of the atom cloud into the resonator. We present the

design and the fabrication of this atom chip.

The completed setup will enable investigations of the interplay of spin-dynamics in

presence of light mediated correlations and spin-squeezing at a metrologically relevant

stability level of 10^(−13) at 1 s.
22 juin 2016 (Palaiseau) - Soutenance de thèse de Matthieu DUPONT-NIVET : "Vers un accéléromètre atomique sur puce"

Soutenance le 22 juin 2016 à 14h00 dans l’auditorium de l’Institut d’Optique – Campus Polytechnique 2 avenue Augustin Fresnel 91127 Palaiseau , juste en face de Thales Research and Technology)

devant un jury composé de : Christoph Westbrook – Hélène Perrin – Ernst Rasel – Jakob Reichel – Eric Charron – Sylvain Schwartz – Philippe Adam

Nous rapportons les développements, théoriques et expérimentaux, visant à la réalisation d’un accéléromètre à atomes froids. Cet interféromètre utilise un gaz ultra froid non-dégénéré qui est piégé au voisinage d’une puce atomique pendant toute la séquence d’interrogation. Nous décrivons un protocole d’interrogation permettant de rendre le capteur sensible aux accélérations. Ce protocole est constitué d’une séquence de Ramsey avec une séparation spatiale des deux états de l’interféromètre. Le signal et le contraste de cet interféromètre sont modélisés et l’utilisation de raccourci à l’adiabaticité est considérée pour réaliser une séparation et une recombinaison rapide des deux états. Nous décrivons aussi une implémentation de cet interféromètre sur une puce atomique. Elle repose sur la création de deux potentiels habillés micro-onde, un pour chacun des deux états de l’interféromètre. Le dispositif de refroidissement des atomes, mis en place pendant cette thèse, est décrit. Des atomes de rubidium 87 sont refroidis jusqu’à la condensation de Bose-Einstein dans l’état |2,2>. Un protocole de type stimulated Raman adiabatic passage utilisant des champs micro-ondes, permet ensuite de transférer les atomes (condensés ou thermiques) vers l’état |2,1>. Cette source atomique a permis de réaliser des mesures du contraste des franges de Ramsey en fonction de la symétrie des potentiels piégeant les deux états de l’interféromètre. Le temps de décroissance du contraste mesuré permet de valider les développements théoriques sur le contraste de l’interféromètre.
10 June 2016 (Paris) – Thesis defense of Stéphane TREMINE : "Study of Cesium atoms cooling in a 3D speckle laser field and realization of a compact atomic clock".

Defense on Friday, 10 of June 2016 at 10:00 – à l’Observatoire de Paris
6 June 2016 (Besançon) – Thesis defense of Alexandre DIDIER : "Development of ultra-stable Fabry-Perot cavities for new generation optical frequency standards".

Defense on Monday, 6 of June 2016 at 10:00 – Amphi JJ. Gagnepain, Femto-ST, Besançon
12 février 2016 (Paris) - Soutenance HDR de Carlos GARRIDO ALZAR : "Interférométrie optique et atomique dans l'ingénierie d'états quantiques et les mesures de précision".

Soutenance le vendredi 12 février 2016 à 14h00 dans l’Amphithéâtre de l’IAP, à l’Observatoire de Paris, Paris

Dans cet exposé, je vous présenterai mes travaux de recherche dont l’objectif premier est le développement de capteurs inertiels quantiques compacts basés sur l’interférométrie atomique. Cette thématique se situe à la jonction de sujets de recherche sur lesquels j’ai travaillé pendant mes séjours postdoctoraux. Lors de mon premier postdoc j’ai travaillé à la mise en place théoretiquement et expérimentalement d’un protocole d’ingénierie d’états quantiques atomiques pour la métrologie et les mesures de haute précision. Cette recherche visait, en particulier, à l’amélioration de la précision d’une horloge atomique de césium en utilisant un ensemble d’atomes froids préparés dans un état où ils sont fortement corrélés. Je vous parlerai du protocole utilisé, fondé sur les mesures quantiques non destructives, et qui nous a permis d’observer en temps réel un dynamique quantique cohérente sur un même ensemble d’atomes.

Ma présentation se poursuivra avec une discussion sur les puces ou microcircuits à atomes. J’aborderai les avantages de ces dispositifs, la problématique spécifique à leur utilisation pour l’interférométrie atomique et les possibles solutions que nous avons déjà testé et envisagé dans ce contexte. En particulier, je vous parlerai sur le problème de décohérence observé dans le piégeage et guidage de nuages d’atomes froids, ainsi que sur la technique de modulation mise au point pour nous affranchir de celui-ci.

Je terminerai l’exposé avec la présentation de mon programme de recherche sur l’instrumentation de capteurs inertiels à atomes froids guidés sur microcircuit à atomes. Les éléments clefs à la réalisation de ces dispositifs pour le mesures de précision seront analysés. En particulier, je vous présenterai les critères importants à observer pour leur potentielles applications dans la navigation inertielle, les mesures géophysiques et les tests de physique fondamentale.
27 jan. 2016 (Paris) - "Study and realization of a new spatio-temporal reference system based on inter-satellite links in a GNSS constellation"

Defense on Wednesday, 27 of January 2016 at 14:30 – l’amphithéâtre de l’IAP, Observatoire de Paris

Work accomplished in SYRTE under the supervision of Peter WOLF and Pacôme DELVA

The accuracy reached by the Global Navigation Satellite Systems (GNSS) is critically important for many scientific applications such as geodetic point or satellite positioning, space-time reference frame realization, clocks synchronization or the study of the links to probe the atmosphere. One option for improving the system accuracy is the use of inter-satellite pseudo-range measurements, so called inter-satellite links (ISL). Several studies have shown the qualitative interest of ISL but do not allow to efficiently measure the quantitative impact of this new technology on space-time positioning. In this thesis, we present a differential study between a standard system (with standard satellite-to-ground links only) and system augmented by ISL. The two systems are compared under the same hypothesis and simulated within the same software. The software is made of two distinct and independent parts : the simulation which generates the noisy pseudo-ranges, and an analysis which uses a non linear adjustment procedure in order to recover the initial parameters of the simulation and compute the quantitative error budgets. For a given application, the quantitative comparison between the error budgets of both systems allow us to highlight the relative merits of the two configurations. Our results are a further step in the characterization of the interest of ISL and should prove useful for the design of future satellite navigation system design.
14 dec. 2015 (Villetaneuse) - Thesis defense of Anthony BERCY, « Ultrastable optical fiber link: multiple-users dissemination, study of fundamental and technological limits and new applications »

Defense on Monday 14 December 2015 at 14:00 – Amphithéâtre Euler, Université PAris 13, Villetaneuse

Work accomplished within a collaboration between LPL and SYRTE.

“Optical frequency links give the possibility to disseminate an ultra-stable frequency reference to many research laboratories for precise measurements as performed in frequency metrology and in applied and fundamental physics. We demonstrated first a simple branching network setup dropping an ultra-stable signal at different positions along an urban optical link of 92 km, that exhibits a relative frequency stability of 1.3×10-15 at 1 s integration time, limited by long-term diurnal thermal effects. We developed and tested an improved setup with a compact and thermalized optical interferometer and a laser diode used to feed a secon- dary link, which fiber noise is compensated. These two setup open the way to multiple-users dissemination in Paris area and on the REFIMEVE+ network.

Second we demonstrated optical frequency comparison using a two-way method. We tested the sensitivity of this comparison over a 100 km telecommunication fiber loop network using either unidirectional or bidirectional propagation, with an excellent frequency stability thanks to the very good rejection of the fiber noise.

These results open the way to high-resolution frequency comparison of the best optical clocks over national or international fiber networks.”
09 dec. 2015 (Besançon) - Thesis defense of Irina BALAKIREVA "Non-linear dynamics of Kerr optical frequency combs"

Defense on Wednesday december 9th, – 14:00 in Amphithéâtre Jean-Jacques Gagnepain (bât. Témis Sciences), 15B avenue des Montboucons, Besançon

Work accomplished in FEMTO-ST under the supervision Yanne Chembo et Laurent Larger

Thesis dedicated to the study of Kerr optical frequency combs generated in whispering gallery mode resonators.
03 dec. 2015 (Nice) - Thesis defense of Liwei WEI, « High-Power Laser System for Advanced Virgo Gravitational Wave Detector: Coherently Combined Master Oscillator Fiber Power Amplifiers »

Defense on Thursday 03 December 2015 at 10:00 – Mt Gros, Observatoire de la Côte d’Azur, Bd de l’Observatoire , Nice (salle de la Nef)

Work accomplished in ARTEMIS

Virgo is a cavity-enhanced Michelson interferometer built for the direct detection of gravitational waves. The Advanced Virgo project consists of major upgrades to the Virgo gravitational wave detector for an order of magnitude improvement in differential strain sensitivity, one of which is the tenfold increase in injected laser power to 175 Watts. The use of fiber laser amplifiers and their coherent combination are foreseen to deliver the required high-power low-noise beam. In this thesis work, we review the laser requirements for gravitational wave detectors, introduce the design of the laser system for Advanced Virgo, and develop the means for laser characterization in accordance with the stringent noise specifications. We then present the results to date, notably the quasi-continuous long-term operation of two 40-Watt fiber laser amplifiers over thousands of hours and their coherent combination with Mach-Zehnder interferometry. Although the targeted power for Advanced Virgo is not yet attained, the developed system shows decent noise performance and is promising for further power-scaling efforts.

Keywords : laser characterization, fiber laser amplifier, coherent beam combination, interferometry, gravitational wave detector
27 nov. 2015 (Palaiseau) - PhD defense of Fabien THERON, “Development of a cold atom gravity gradiometer and a telecom doubled laser device for onboard applications”

Defense on Friday 27 November 2015 at 14:00 – Institut d’Optique Graduate School (Auditorium), Palaiseau

Work accomplished in ONERA

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
26 nov. 2015 (Paris) - Seminar - Kurt Gibble (Penn State University, USA), « Sundry Topics on Atomic Clocks »

Seminar on Thursday 26 November 2015 at 11:00 – SYRTE, PAris Observatory (Salle de l’atelier)

I’ll discuss diverse, recent work from our group. One result is our precision measurements of s-wave quantum scattering phase shifts of ultra-cold atoms in a cesium fountain. With mrad precision, we observe a series of Feshbach resonances with variations of s-wave phase shifts approaching pi. I’ll also discuss the microwave lensing frequency shift, the recent associated controversy and a connection to recoil shifts, and some unique aspects of the microwave lensing shift of PHARAO. The distributed cavity phase (1st order Doppler) shifts of PHARAO are also significantly different than those of fountains. I will discuss those as well as our plans for a Cadmium optical lattice clock.
23 nov. 2015 (Orsay) - PhD defense of Alexis BONNIN : ” Dual-Species Atom Interferometry and Applications to Inertial Measurements ”

Defense on Monday 23 November 2015 at 14:00 – Laboratoire Aimé Cotton (Salle Balmer), Orsay

Work accomplished in ONERA

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.
20 nov. 2015 (Paris) - PhD defense of Indranil DUTTA : ” tability Improvement of a Sagnac Cold Atom Interferometer: towards Continuous Operation “

Defense on Friday 20 November 2015 at 14:30 – Observatoire de Paris (Amphi de l’IAP), 77 avenue Denfert-Rochereau, Paris

Work accomplished in ONERA

This thesis aims at pushing the performances of a cold atom interferometer principally sensitive to rates of rotation in a particular axis. In our experiment, Cesium atoms are laser cooled, trapped and launched in a fountain configuration. According to the Sagnac effect, the sensitivity of the interferometer to rotation is proportional to the area enclosed by the interferometer arms. We use stimulated Raman transitions to split the atoms in two paths and to form a folded Mach-Zehnder-like interferometer architecture using four Raman pulses. With an interrogation time of the atoms of 800 ms, we achieve a Sagnac area as high as 11 cm2. The thesis describes the improvements to the experimental setup to operate the gyroscope with such a high Sagnac area. A procedure for the relative alignment of the Raman beams at the μrad level is presented, which is critical to meet the interference condition of the cold atoms at the interferometer output. The characterization and mitigation of the vibration noise, affecting the gyroscope, is also demonstrated. We finally demonstrate a short term rotation stability of 160 nrad/s at 1 s and a long term stability of 1.8 nrad/s after 10000 s of integration time. This stability level represents a factor 5 improvement compared to the previous SYRTE gyroscope experiment of 2009 and a factor 15 compared to other published results. The thesis work also presents a new method of interrogation to operate the gyroscope without dead times, which is important for various applications of cold atom sensors in inertial navigation, geophysics and in fundamental physics.

Keywords: Atom interferometry, cold atoms, gyroscope, Sagnac effect, stimulated Raman transitions, inertial sensor