E. de Clercq

OSCC project : A space Cs beam optically pumped atomic clock for Galileo

Thales electron devices has been pursuing since 2003 frequency standards activities. In the framework of these activities, Thales established a consortium for the development of a space Cs atomic clock for Galileo. This consortium is composed by two of the best scientific laboratories in the European Time-Frequency community : the Observatoire de Neuchatel (ON) and the SYRTE Observatoire de Paris, and by two space industrials : Oerlikon space AG (OSAG) and Thales Electron Devices. The name of the project is OSCC for Optically pumped Space Cs Clock. The first phase (phase A) of this development started in June 2006 under an ESA contract. The purpose of this phase A is a feasibility study of Cs clock technology for Galileo with the manufacturing and the test of a new compact optically pumped Cs clock breadboard. This technology is well known in laboratories but it has never been industrialized, even for ground applications. This study starts with a strong background at SYRTE and ON, but also with new industrial developments realized at Thales during the last years. Frequency stability in order of 1 to 3times10-12 . tau-1/2 has been already demonstrated in lab with different configurations. This document will first synthesize the last results obtained by each Partner, followed by the results of the existing hardware analysis performed in the first step of the project. This analysis allowed Partners to share their know-how and to identify the limits of each existing breadboards with respect to the objectives of the project. As a result of this analysis, it was possible to define the atomic resonator best configuration for each subsystem. At least, this document presents a few design drivers of the new OSCC devices.

Probe light-shift elimination in generalized hyper-Ramsey quantum clocks

We present a new interrogation scheme for the next generation of quantum clocks to suppress frequency-shifts induced by laser probing fields themselves based on Generalized Hyper-Ramsey resonances. Sequences of composite laser pulses with specific selection of phases, frequency detunings and durations are combined to generate a very efficient and robust frequency locking signal with almost a perfect elimination of the light-shift from off resonant states and to decouple the unperturbed frequency measurement from the lasers intensity. The frequency lock point generated from synthesized error signals using either

Frequency Stability Measurement of a Raman-Ramsey Cs Clock

\pi/4

Quantum engineering of atomic phase shifts in optical clocks

or

Coherent population trapping with cold atoms

3\pi/4

An analysis of major frequency shifts in the LPTF optically pumped primary frequency standard

laser phase-steps during the intermediate pulse is tightly protected against large laser pulse area variations and errors in potentially applied frequency shift compensations. Quantum clocks based on weakly allowed or completely forbidden optical transitions in atoms, ions, molecules and nuclei will benefit from these hyper-stable laser frequency stabilization schemes to reach relative accuracies below the 10

Progress on a pulsed CPT clock: Reduction of the main noise source contributions

^{-18}

High performance compact atomic clock based on coherent population trapping

level.

In-depth analysis of the frequency stability of optically pumped cesium beam frequency standards

CPT clocks are studied worldwide as miniature frequency standards for portable applications. To improve their frequency stability, we have investigated the optimum operating conditions (cell temperature, laser intensity, interrogation method) and measured the corresponding frequency shifts and stability. Compared to the continuous CPT interrogation, the pulsed interrogation reduces the light shift by a factor 300 and improves the frequency stability by a factor 10. The short term frequency stability is 9 x 10 -3 at 1 s, limited to 2 x 10 -3 after 300 s.

Latest achievements on the pulsed CPT clock

Quantum engineering of time-separated Raman laser pulses in three-level systems is presented to produce an ultranarrow optical transition in bosonic alkali-earth clocks free from light shifts and with a significantly reduced sensitivity to laser parameter fluctuations. Based on a quantum artificial complex wave-function analytical model and supported by a full density-matrix simulation including a possible residual effect of spontaneous emission from the intermediate state, atomic phase shifts associated with Ramsey and hyper-Ramsey two-photon spectroscopy in optical clocks are derived. Various common-mode Raman frequency detunings are found in which the frequency shifts from off-resonant states are canceled, while their uncertainties at the 10−18 level of accuracy are strongly reduced.