Defenses – Seminars
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 P3w/Pw > 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-1/2 with a minimum value of 6 x 10-15 from 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
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).
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.
1st 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.
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.
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 5.710-9g/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 610-11g 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
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
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
“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 ONERAThis 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