500-Hz two-photon Ramsey fringes with a SF6 beam: towards a new frequency standard in the 30-THz spectral region

Shelkovnikov, A.; Grain, Ch.; Nguyen, C.T.-C.; Butcher, R.J.; Amy‐Klein, Anne; Chardonnet, Ch.

doi:10.1007/s003400100628

Cited by 11 publications

(5 citation statements)

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“…Indeed this is particularly significant for a potential standard. The current measurements are smaller than those earlier reported [9] for a He-seeded beam, which is undoubtedly due to the resolution. Most importantly the saturation power varies with hyperfine component.…”

Section: Light Shiftcontrasting

confidence: 49%

“…Given the absolute scale, this small effect can be investigated and results are reported. The two-photon Ramsey fringe experiment employing a supersonic beam of SF 6 has been developed over number of years and is already described in some detail [7][8][9][10]. In brief, the molecular beam interacts successively with two standing waves, which are tuned to a two-photon resonance.…”

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confidence: 99%

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Two-photon Ramsey fringes at 30 THz referenced to an H maser/Cs fountain via an optical-frequency comb at the 1-Hz level

Shelkovnikov

Grain

Butcher

et al. 2004

IEEE J. Quantum Electron.

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Index Terms--Carbon dioxide lasers, Frequency stability, SF 6 , Optical frequency standard. I. INTRODUCTIONThe carbon dioxide laser has given to the 30 THz spectral region particular significance in frequency metrology. The current standard at 30THz is provided by the CO 2 laser locked onto a saturated absorption resonance of OsO 4 in a cell, the reference signal having full width half maximum (FWHM) of 20 kHz [1,2]. The same area is particularly rich in molecular spectra and many problems in this area, together with questions of fundamental physics, have been investigated using the related saturation spectroscopy [3,4]. Typical linewidths are 1-100 kHz. This paper presents continuing work on a two-photon Ramsey fringe experiment on a supersonic beam of SF 6 with the objectives, now essentially realized, of resolving the entire complex hyperfine structure over some 50 kHz and establishing absolute frequencies at the 1Hz level. Both aspects represent huge advances over cell saturation techniques. Two experimental developments have led to the recent advances. First, the distance between the absorption zones has been increased to 1m, so that the fringe periodicity is now 200 Hz for pure SF 6 . Data is routinely recorded with a signal-to-noise ratio (SNR) of 20 in a bandwidth of 1 Hz. The implied limit on the resolution of two components within the hyperfine structure of the SF 6 spectrum is only 10Hz. This is indeed found when fringe patterns are fitted. Second the entire system can now be directly related to the frequency comb of a femtosecond laser, itself referenced to a Hydrogen maser. The maser is compared to a Caesium fountain and to the GPS system. This gives a long-term stability and frequency reproducibility limited by the performance of the current electronics, various optical links and, possibly, the reference maser. The fs technology is necessarily operated in a new area of precision, comparable with the best currently in use [5,6]. Figure 1 gives a block outline of the entire experiment.Two related series of experiments are presented. First the central Ramsey fringe is employed as the reference point for a molecular clock; the clock frequency is measured, and its performance established, relative to the H maser. Second, and separately, Ramsey fringes are measured on an absolute frequency scale provided by the H maser. This gives a second measurement of the central fringe and the entire spectrum of Ramsey fringes over 50 kHz is put onto an absolute frequency scale.This work is partly directed at a new frequency standard. Since a two-photon transition is used the absolute frequency depends on the optical power. Given the absolute scale, this small effect can be investigated and results are reported.

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Section: Light Shiftcontrasting

confidence: 49%

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confidence: 99%

Two-photon Ramsey fringes at 30 THz referenced to an H maser/Cs fountain via an optical-frequency comb at the 1-Hz level

Shelkovnikov

Grain

Butcher

et al. 2004

IEEE J. Quantum Electron.

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“…For the demonstration of the method, we focus our attention on a P(55) line of 190 OsO 4 near the P(16) CO 2 laser line, the frequency of which is already well-known. It is located at 59.070 MHz from the CO 2 line centre and was recently used as a reference for the measurement of two-photon absorption line in SF 6 [16]. Its absolute frequency ν ref =28412648819596 (45) Hz is calculated from two independent measurements.…”

Section: Resultsmentioning

confidence: 99%

Absolute frequency measurement in the 28-THz spectral region with a femtosecond laser comb and a long-distance optical link to a primary standard

Amy‐Klein

Goncharov

Daussy

et al. 2004

Applied Physics B: Lasers and Optics

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A new frequency chain was demonstrated to measure an optical frequency standard based on a rovibrational molecular transition in the 28 THz spectral region accessible to a CO 2 laser. It uses a femtosecond-laser frequency comb generator and two laser diodes at 852 nm and 788 nm as intermediate oscillators, with their frequency difference phase-locked to the CO 2 laser. The RF repetition rate of the femtosecond laser was compared with a 100-MHz signal from a Hydrogen Maser, located at BNM-SYRTE. The 100 MHz signal is transmitted by amplitude modulation of a 1.55 µm laser diode through a 43-km telecommunication optical fibre. As a first example, the absolute measurement of a saturation line of OsO 4 in the vicinity of the P(16) laser line of CO 2 is reported with a relative uncertainty of 10-12 , limited by the CO 2 /OsO 4 frequency day-today reproducibility. The current limit on the stability of the frequency measurement is 4×10-13 at 1 s.

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“…In this context, molecular-beam spectroscopy using a two-photon Ramsey-fringes experiment, [65,66] recently developed in Villetaneuse, seems to be very promising and should allow us to reach a precision of 0.01 Hz on the frequency difference between the two enantiomers. The principle of this experiment is to generate a supersonic beam of chiral molecules which expands in a highvacuum chamber.…”

Section: New Experimental Program Pv Experimentsmentioning

confidence: 98%

Search for Resolution of Chiral Fluorohalogenomethanes and Parity‐Violation Effects at the Molecular Level

et al. 2003

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The first observation of a parity-violation effect in molecules induced by weak interactions is still a dream that requires the synthesis and, eventually, the resolution of the enantiomers of well-chosen simple chiral molecules together with an appropriate experimental set-up for high-resolution spectroscopy. Performing IR spectroscopy on highly enantiomerically enriched samples of bromochlorofluoromethane succeeded in giving an upper limit of 10(-13) for the relative vibrational energy difference between the two enantiomers. These results led us to conceive a new experimental set-up based on a supersonic molecular beam and to work on other chiral molecules, such as chlorofluoroiodomethane. A synthesis of (+/-)-CHCIFI from racemic chlorofluoroiodoacetic acid should, in the near future permit the preparation of optically active samples of this haloform. The development of molecular beam spectroscopy using a two-photon Ramsey-fringes experiment should allow us to reach the precision needed to observe parity violation. These experimental challenges, which stimulate a close collaboration between chemists and physicists, are presented. The success of these projects would open the route to new information on the molecular Hamiltonian, a better knowledge of the electroweak interaction, and a better control of the various chirality-related properties of simple molecules.

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500-Hz two-photon Ramsey fringes with a SF6 beam: towards a new frequency standard in the 30-THz spectral region

Cited by 11 publications

References 0 publications

Two-photon Ramsey fringes at 30 THz referenced to an H maser/Cs fountain via an optical-frequency comb at the 1-Hz level

Two-photon Ramsey fringes at 30 THz referenced to an H maser/Cs fountain via an optical-frequency comb at the 1-Hz level

Absolute frequency measurement in the 28-THz spectral region with a femtosecond laser comb and a long-distance optical link to a primary standard

Search for Resolution of Chiral Fluorohalogenomethanes and Parity‐Violation Effects at the Molecular Level

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