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Study of microwave cavities for high performance pulse pumped double resonance atomic clocks

English title Study of microwave cavities for high performance pulse pumped double resonance atomic clocks
Applicant Skrivervik Anja
Number 162346
Funding scheme Project funding
Research institution Laboratoire d'électromagnétisme et antennes EPFL - STI - IEL - LEMA
Institution of higher education EPF Lausanne - EPFL
Main discipline Electrical Engineering
Start/End 01.11.2015 - 31.01.2018
Approved amount 316'140.00
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All Disciplines (2)

Discipline
Electrical Engineering
Other disciplines of Physics

Keywords (5)

frequency standards; microwave cavities; vapor cells; atomic clocks; field homogeneity

Lay Summary (French)

Lead
Ce projet de recherche concerne l’étude d’un nouveau type de cavités micro-ondes pour application dans des étalons de fréquence à cellule de Rubidium compacts de de hautes performances, fonctionnant notamment en régime pulsé. Ces horloges atomiques dont le volume est inférieur à 5 litres sont des instruments essentiels pour des applications-clef nécessitant des références mobiles garantissant de stabilités de l’ordre de 1 ns par jour, ce qui correspond à une stabilité relative de fréquence d’environ 10 puissance -14 par jour.
Lay summary

Dans un étalon de fréquence au Rubidium fonctionnant selon le principe de la Double Résonance (DR), la vapeur atomique est soumise à un champ micro-onde précisément accordé en fréquence sur une transition hyperfine.  Que ce champ soit appliqué de manière continue ou pulsée, il est essentiel de contrôler précisément la distribution spatiale de ce champ à travers la cellule qui contient la vapeur afin d’optimiser le signal de résonance et obtenir une stabilité au niveau de l’état de l’art. Ceci peut être obtenu grâce à une cavité micro-onde. Toute imperfection au niveau de la directivité et/ou de l’homogénéité du champ micro-onde peut se traduire en un effet systématique qui dégrade les performances à court, moyen ou long terme de l’étalon de fréquence.

L’approche du Pompage Optique Pulsé (POP) présente certains avantages par rapport au pompage optique continu mais renforce ultérieurement les exigences en terme d’homogénéité spatiale du champ micro-onde car elle exige que chaque atome dans la vapeur subisse exactement un «pulse pi/2» (rotation du spin fictif associé de 90°, selon la terminologie de la Résonance Magnétique Nucléaire). Or les cavités actuelles ne permettent pas d’obtenir une telle homogénéité à travers toute la cellule de Rubidium, tout en maintenant un volume total réduit.

Dans ce nouveau projet, l’objectif est de réaliser des cavités micro-ondes dont le champ approche une distribution idéale tout en maintenant une taille compacte.

Il s’agit d’un projet en collaboration entre le LEMA-EPFL, responsable de la conception, réalisation et caractérisation des cavités micro-onde et le LTF-UniNe, responsable de la spectroscopie atomique, et de la métrologie « Temps-Fréquence ». Un modèle théorique sera d’abord développé afin de prédire les performances de la future horloge. Une première validation expérimentale du modèle est prévue avec les cavités micro-ondes existantes. Durant une seconde étape, le modèle servira de base au développement d’une nouvelle cavité micro-onde.

Direct link to Lay Summary Last update: 26.10.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Characterization of Frequency-Doubled 1.5- $\mu$ m Lasers for High-Performance Rb Clocks
Almat Nil, Moreno William, Pellaton Matthieu, Gruet Florian, Affolderbach Christoph, Mileti Gaetano (2018), Characterization of Frequency-Doubled 1.5- $\mu$ m Lasers for High-Performance Rb Clocks, in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 65(6), 919-926.
Rb vapor-cell clock demonstration with a frequency-doubled telecom laser
Almat Nil, Pellaton Matthieu, Moreno William, Gruet Florian, Affolderbach Christoph, Mileti Gaetano (2018), Rb vapor-cell clock demonstration with a frequency-doubled telecom laser, in Applied Optics, 57(16), 4707-4713.
3D printed microwave cavity for atomic clock applications: proof of concept
Pellaton M, Affolderbach Christoph, Skrivervik Anja K., Ivanov Anton E., Debogovic T., Rijk E. de, Mileti Gaetano (2018), 3D printed microwave cavity for atomic clock applications: proof of concept, in Electronics Letters, 54(11), 691-693.
Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications
Affolderbach Christoph, Moreno W., Ivanov Anton E., Debogovic T., Pellaton M, Skrivervik Anja K., Rijk E. de, Mileti Gaetano (2018), Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications, in Applied Physics Letters, 112(11), 113502.
Impact of static-magnetic-field-gradients on relaxation times in a Rb vapor cell
Gharavipour Mohammadreza, Affolderbach Christoph, Gruet Florian, Mileti Gaetano, Radojicic Ivan S., Krmpot Aleksandar J., Jelenkovic Brana M. (2017), Impact of static-magnetic-field-gradients on relaxation times in a Rb vapor cell, in 2017 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Cont, 57-59.
Optically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor
Gharavipour M, Affolderbach C, Gruet F, Radojičić I S, Krmpot A J, Jelenković B M, Mileti G (2017), Optically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor, in New Journal of Physics, 19(6), 063027-063027.
Design of atomic clock cavity based on a loop-gap geometry and modified boundary conditions
Ivanov Anton E., Affolderbach Christoph, Mileti Gaetano, Skrivervik Anja K. (2017), Design of atomic clock cavity based on a loop-gap geometry and modified boundary conditions, in International Journal Of Microwave And Wireless Technologies, 9(7), 1373-1386.
Compact microwave cavity with increased magnetic field homogeneity
Ivanov A. E., Skrivervik A. K., Affolderbach C., Mileti G. (2016), Compact microwave cavity with increased magnetic field homogeneity, in 2016 10th European Conference on Antennas and Propagation (EuCAP), Davos1-5, EurAAP, Davos1-5.
Study of field misalignment in a cavity used for atomic clock applications
Ivanov A. E., Affolderbach C., Mileti G., Skrivervik A. K. (2016), Study of field misalignment in a cavity used for atomic clock applications, in 2016 URSI International Symposium on Electromagnetic Theory (EMTS), Helsinki308-311, URSI, Helsinki308-311.

Collaboration

Group / person Country
Types of collaboration
Istituto Nazionale in Ricerca e Metrologia, Torino Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. P. Treutlein, Universität Basel Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
VIII International Symposium Modern Problems of Laser Physics Talk given at a conference Ramsey spectroscopy in vapour-cells for compact high-performance atomic clocks (invited) 25.08.2018 Novosibirsk, Russia Mileti Gaetano;
2018 IEEE International Frequency Control Symposium Talk given at a conference Selected studies on high performance laser-pumped Rubidium atomic clocks 22.05.2018 Squaw Creek, Olympic Valley, CA, United States of America Mileti Gaetano;
32nd European Frequency and Time Forum 2018 Talk given at a conference Ramsey-Mode Rb Cell Clock Demonstration with a 3D-Printed Microwave Cavity 10.04.2018 Torino, Italy Mileti Gaetano;
Annual Meeting of the Swiss Physical Society Talk given at a conference Laser-pumped high performance vapor-cell atomic clocks (invited) 21.08.2017 Geneva, Switzerland Mileti Gaetano;
European Frequency and Time Forum and International Frequency Control Symposium Talk given at a conference Cell-Based Stabilized Laser Sources and Light-Shifts in Pulsed Rb Atomic Clocks 10.07.2017 Besançon, France Mileti Gaetano; Gharavipour Mohammadreza;
European Frequency and Time Forum and International Frequency Control Symposium Talk given at a conference Impact of Static-Magnetic-Field-Gradients on Relaxation Times in a Rb Vapor Cell 10.07.2017 Besançon, France Mileti Gaetano; Gharavipour Mohammadreza;
Joint 2017 International Frequency Control Symposium and European Frequency and Time Forum Talk given at a conference Impact of Static-Magnetic-Field-Gradients on Relaxation Times in a Rb Vapor Cell 09.07.2017 Besançon, France Mileti Gaetano; Gharavipour Mohammadreza;
3rd URSI Regional Conference on Radio Science Talk given at a conference High performance and miniature laser-pumped vapour-cell frequency standards (invited plenary talk) 01.03.2017 Tirupati, India Mileti Gaetano;
Annual Meeting of the Swiss Physical Society Talk given at a conference Comparison of relaxation times in a Rb vapor-cell measured with different methods 23.08.2016 Lugano, Switzerland Mileti Gaetano; Gharavipour Mohammadreza;
URSI International Symposium on Electromagnetic Theory (EMTS) Talk given at a conference Study of field misalignment in a cavity used for atomic clock applications 14.08.2016 Espoo, Finland Ivanov Anton Evgeniev;
10th European Conference on Antennas and Propagation Poster Compact Microwave Cavity with Increased Magnetic Field Homogeneity 10.04.2016 Davos, Switzerland Ivanov Anton Evgeniev; Skrivervik Anja;
30th European Frequency and Time Forum Poster Light Shifts Studies in CW and Ramsey Double Resonance Vapor Cell Frequency Standards 04.04.2016 York, Great Britain and Northern Ireland Gharavipour Mohammadreza; Mileti Gaetano;
30th European Frequency and Time Forum Poster Study of the Misalignment between Electromagnetic Fields Interacting with Rb Atoms in a Cavity with Losses 04.04.2016 York, Great Britain and Northern Ireland Mileti Gaetano; Gharavipour Mohammadreza; Ivanov Anton Evgeniev;
30th European Frequency and Time Forum Poster Microwave Cavity Characterization for Rubidium Frequency Standards 04.04.2016 York, Great Britain and Northern Ireland Gharavipour Mohammadreza; Mileti Gaetano;
30th European Frequency and Time Forum Talk given at a conference Relaxation Time Measurements in a Rb Vapor Cell 04.04.2016 York, Great Britain and Northern Ireland Mileti Gaetano; Gharavipour Mohammadreza;


Communication with the public

Communication Title Media Place Year
Print (books, brochures, leaflets) 3D printing for atomic clocks International 2016

Associated projects

Number Title Start Funding scheme
156621 Precision double resonance spectroscopy and metrology with stabilised lasers and atomic vapours: applications for atomic clocks and magnetometers 01.01.2015 Project funding
140712 Microwave Cavities for High Performance Double Resonance Atomic Clocks and Sensors 01.11.2012 Project funding
128704 Systèmes pour revêtement de cellules à alcalins pour horloges atomiques 01.06.2010 R'EQUIP

Abstract

This research proposal concerns the study of novel types of microwave cavities, for applications in compact and high-performance vapor-cell atomic clocks, and more particularly in such atomic clocks operated in the pulsed optically pumped scheme. Such compact vapor-cell atomic clocks (volumes < 5 liters) are the instruments of choice in many of today’s key applications where excellent timing and frequency stability on the level of = 1 ns/day (relative frequency stability = 1x10^-14/day) are required from a small and mobile system. In both continuous-wave (cw) and pulsed double-resonance (DR) vapor-cell atomic clocks, precise control of the microwave field distribution across the atomic sample held in the vapor cell is required, in order to achieve a strong atomic signal with high quality factor, and thus state-of-the-art short-term clock stability. Generally, a microwave cavity resonator is used for this purpose in a vapor-cell clock. Similarly, imperfections in the directivity and homogeneity of the applied microwave field can result in position-dependent systematic effects (e.g. such as microwave power shifts) that can degrade the long-term clock stability. The control and optimization of the microwave field distribution in the cavity resonator used is thus critical for assuring the best possible stability performance of a vapor-cell clock. In the pulsed optically pumped (POP) approach, the homogeneity of the microwave field amplitude over the entire atomic sample is of strongly increased importance, because all atoms should undergo near-perfect pi/2-pulses to take full advantage of this clock scheme. In existing present studies this is achieved by making the atomic vapor cell occupy only a small fraction of the microwave cavity, making the overall clock package rather bulky. It is thus of interest to achieve a close to ideal field distribution from a cavity as small as possible, in order to keep the overall clocks small and of interest for distributed and/or mobile applications. In previous work of the applicants, novel microwave cavities based on the loop-gap resonator approach (LGR, also known as magnetron-type resonator) have been developed and studied, including their applications in cw DR atomic clocks. In this present project proposal, we will extend this work to also study specifically novel microwave cavities based on the same LGR approach, but optimized for clock operation in the POP clock scheme. The project goal is thus to develop and study a novel microwave cavity for a POP clock, with close to ideal field distribution and as small size as possible, and to experimentally evaluate the impact of such cavities on the atomic clock performance. For this purpose we propose a collaborative research approach, in which EPFL-LEMA contributes its expertise in microwave system design, prototyping, studies, and characterization, and UniNe-LTF contributes its expertise in atomic spectroscopy, atomic clock physics, and metrology. In a first project step, a theoretical model will be developed in order to allow making clock performance predictions for a given microwave field distribution in the cavity. In a second step, this model will then be used to develop a new, highly compact, and optimized LGR cavity for the POP clock, including a new tuning scheme for the resonance frequency. The model will also be validated experimentally by experimental clock studies with existing microwave resonators. Finally, a prototype of the new optimized LGR cavity will be realized and studied.
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