We report the observation of Raman-Ramsey fringes using a double lambda scheme creating coherent population trapping in an atomic ensemble combined with pulsed optical radiations. The observation was ...made in a Cs vapor mixed with N2 buffer gas in a closed cell. The double lambda scheme is created with lin perpendicular lin polarized laser beams leading to higher contrast than the usual simple lambda scheme. The pulsed trapping technique leads to narrow fringe widths scaling as 1/(2T) with high contrasts which are no longer limited by the saturation effect. This technique operates in a different way from the classical Ramsey sequence: the signal is done by applying a long trapping pulse to prepare the atomic state superposition, and fringe detection is accomplished by optical transmission during a short second trapping pulse without any perturbation of the dark state.
We have developed an atom interferometer providing a full inertial base. This device uses two counterpropagating cold-atom clouds that are launched in strongly curved parabolic trajectories. Three ...single Raman beam pairs, pulsed in time, are successively applied in three orthogonal directions leading to the measurement of the three axis of rotation and acceleration. In this purpose, we introduce a new atom gyroscope using a butterfly geometry. We discuss the present sensitivity and the possible improvements.
HORACE (HOrloge à Refroidissement d’Atomes en Cellule
=
clock based on atoms cooled from vapour cell) is a compact cold caesium atom clock developed in SYRTE at Paris Observatory. This clock can ...operate both on ground and in microgravity environment. Design of HORACE is based on isotropic light cooling, allowing performing the whole clock sequence (cooling, atomic preparation, Ramsey interrogation and detection) at the same place. Compared to more conventional cold atom clocks such as atomic fountains, the use of isotropic light cooling simplifies both the optical part of the setup and the detection sequence, and leads to a drastic size reduction of the physics package. Very good short-term performances have been demonstrated at SYRTE since relative frequency instability of 2.2
×
10
−13
τ
−1/2 has been obtained. Optimization of the long term stability is still under progress and current results show relative frequency instability around 3
×
10
−15 in 10
4
s of integration. With these performances, HORACE appears as a good candidate both for Galileo’s ground segment clock and for onboard Galileo clock.
Current Status of a Pulsed CPT Cs Cell Clock Boudot, R.; Guerandel, S.; de Clercq, E. ...
IEEE transactions on instrumentation and measurement,
04/2009, Letnik:
58, Številka:
4
Journal Article
Recenzirano
A Raman-Ramsey Cs cell atomic clock is presented. The relaxation times of the population and the hyperfine coherences in the cell are measured. The effect on the central Ramsey fringe amplitude of ...the critical experimental parameters such as laser intensity, magnetic field, temperature, and Ramsey time is investigated. The existence and impact of the additional Deltam = 2 transitions involved in the pumping scheme are pointed out. Narrow resonance linewidths as low as 33 Hz with reasonable signal-to-noise ratios have been recorded. By removing a frequency drift attributed to the cell, the achieved frequency stability is 7 times 10 -13 tau -1/2 . The main noise contributions that limit the short-term frequency stability are reviewed and estimated.
A gas cell atomic frequency standard based on coherent population trapping (CPT) with Ramsey interrogation pulses is developed. The clock resonance is detected in a Cs cell with buffer gas using two ...phase-locked diode lasers tuned to the Dl line. A preliminary short-term stability of 3.5 10 -12 t is reported. The CPT specificity allows a new interrogation-detection sequence, i.e., the continuous pulse train, which, with phase modulation, could lead to better short-term stability compared to usual continuous CPT clocks. The parameters optimizing the stability include a high Rabi frequency, a very short measurement time, and an interrogation time equal to the lifetime of the hyperfine coherence
The Ramsey method has been applied by means of optical coherent population trapping (CPT) pulses through a cesium vapor cell with N/sub 2/ buffer gas at room temperature, using two phase-locked ...lasers. With this method, CPT resonance spectral widths are no longer limited by optical saturation and collision effects, but only depend on free evolution time between the two pulses. A fringe width below 100 Hz is reported. Experimental Raman-Ramsey fringes are analyzed using the classical wavefunction formalism.
In atom interferometry based on light-induced diffraction, the optical aberrations of the laser beam splitters are a dominant source of noise and systematic effect. In an atomic gyroscope, this ...effect is dramatically reduced by the use of two atomic sources. But it remains critical while coupled to fluctuations of atomic trajectories, and appears as a main source of noise to the long term stability. Therefore we measure these contributions in our setup, using cold Cesium atoms and stimulated Raman transitions.
Abstract This paper outlines the roadmap towards the redefinition of the second, which was recently updated by the CCTF Task Force created by the CCTF in 2020. The main achievements of optical ...frequency standards (OFS) call for reflection on the redefinition of the second, but open new challenges related to the performance of the OFS, their contribution to time scales and UTC, the possibility of their comparison, and the knowledge of the Earth’s gravitational potential to ensure a robust and accurate capacity to realize a new definition at the level of 10 −18 uncertainty. The mandatory criteria to be achieved before redefinition have been defined and their current fulfilment level is estimated showing the fields that still needed improvement. The possibility to base the redefinition on a single or on a set of transitions has also been evaluated. The roadmap indicates the steps to be followed in the next years to be ready for a sound and successful redefinition.
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