Potential for improving the Rubidium Frequency Standard with a novel optical pumping scheme using diode lasers

Bhaskar, N. D.

doi:10.1109/58.368318

Cited by 15 publications

(4 citation statements)

References 20 publications

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“…It should be possible to overcome these problems and thus improve the sensitivity by switching to the D 1 line, where, due to the level structure of the excited state, the experimental realisation of an ideal Λ systems is much easier. We are also exploring various other ways of increasing the signal contrast, for instance by optical pumping [20].…”

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confidence: 99%

Picotesla magnetometry with coherent dark states

et al. 2001

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We investigate the experimental sensitivity limit of a scalar optical magnetometer based on coherent population trapping on the D2 line of a thermal cesium vapor. We find the expected strong dependence on averaging time, with a detection limit below 4 pT for integration times longer than 1 s, limited by slow drifts of the cell temperature and of the applied test magnetic-field itself. A detailed noise analysis shows that for shorter averaging times the demonstrated limit of about 12 pT/ √ Hz is dominated by the frequency noise of the laser source. The magnetometer can be operated for real-time detection in flux densities up to at least milliteslas and is robust enough for application outside the laser laboratory.

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confidence: 99%

Picotesla magnetometry with coherent dark states

et al. 2001

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“…These have found a variety of applications in science, telecommunications, industry, and satellite navigation systems (GALILEO, GPS). Schemes developed for the reduction of the LS in such commercial lamp-pumped Rb clocks [9,14] are mostly based on pulsed optical excitation [21,22] while, for laboratory prototype clocks based on laser optical pumping [15,23], the schemes developed rely on spatially separated pump and probe regions [24], pulsed laser pumping [25,26], or two-frequency laser excitation that balances LS contributions of opposite signs [27]. Schemes developed for CPT-based vapour-cell clocks also balance LS contributions of opposite signs, using laser frequency modulation at 3-5 GHz [16,28].…”

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Light-shift suppression in laser optically pumped vapour-cell atomic frequency standards

et al. 2005

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We present a novel scheme for reducing the AC Stark effect in optical-microwave double-resonance spectroscopy and its application for efficient suppression of the light-shift-related instabilities in laser-pumped gas-cell atomic clocks. The method uses a multi-frequency pump light field that can be easily produced by frequency modulation of the single-frequency pump laser. We show theoretically that variations of the light shift with both laser frequency and light intensity can be strongly suppressed with properly chosen pump light spectra. Suitable modulation parameters can be found for both the case of pure frequency modulation as well as for pump light spectra showing amplitude-modulation contributions, as usually found for current modulation of diode lasers. We experimentally demonstrate the method for a Rb atomic clock using a frequency-modulated distributed Braggreflector laser diode as pump light source. IntroductionThe light shift (LS), also known as the AC Stark effect or optical Stark effect, of an atomic level caused by optical probing is a well-known phenomenon. It arises from the interaction of an induced dipole moment with the oscillating electric field of the light, resulting in a shift of the atomic levels and transition frequencies linear with light intensity in the limit of weak fields [1,2]. The existence, control, or reduction of the LS plays a crucial role in many fields of fundamental and applied science, for example Sisyphus [3] and Raman sideband cooling [4][5][6] of atoms in optical lattices [7] or ion-trap quantum information processing [8].The LS also constitutes one of the main sources of instability in such different types of atomic frequency standards [9] as primary atomic fountain clocks [10,11], thermal Cs-beam clocks [12], proposed optical frequency standards [13], and vapour-cell atomic clocks based on optical pumping [14,15] ✉ Fax: +41-32-7220420, E-mail: gaetano.mileti@ne.ch or coherent population trapping (CPT) [16,17]. A number of different approaches have thus been developed to reduce the AC Stark effect in frequency standards. These rely, for example, on mechanical shutters [10,18] or rotating 'light traps' [19] to block unwanted laser light in cold-atom clocks, spatial separation of pump and probe regions in Rb masers [20], or the proposed use of optical lattices at 'magic wavelength' that would balance different LS contributions in optical clocks [13].Here we concentrate on vapour-cell secondary atomic clocks, that offer competitive frequency stabilities both in the short-term (10 −12 to 10 −11 at 1 s) and in the long-term scale (10 −14 to 10 −11 at one day) within a compact (≤ 0.5 to 2.0 l), light (≤ 0.5 to 3.5 kg), and low-power (≤ 8 to 35 W) device. These have found a variety of applications in science, telecommunications, industry, and satellite navigation systems (GALILEO, GPS). Schemes developed for the reduction of the LS in such commercial lamp-pumped Rb clocks [9,14] are mostly based on pulsed optical excitation [21,22] while, for laboratory prototype ...

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“…9,10 As a result, the contrast of resonances, measured in centimeter-sized cells under similar conditions has been near 1%. 11 We note that optical pumping can be used to enhance the atomic population in selected Zeeman states, 12,13 thus increasing the resonance contrast. Because of the added complexity of a setup that requires additional laser beams, the implementation of a small clock based on one of these techniques could be more diff icult.…”

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Dark-line atomic resonances in submillimeter structures

2004

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We present measurements of dark-line resonances excited in cesium atoms confined in submillimeter cells with a buffer gas. The width and contrast of the resonances were measured for cell lengths as low as 100 microm. The measured atomic Q factors are reduced in small cells because of frequent collisions of atoms with the cell walls. However, the contrast of coherent population trapping resonances measured in the small cells is similar in magnitude to that obtained in centimeter-sized cells, but substantially more laser intensity is needed to excite the resonance fully when increased buffer-gas pressure is used. The effect of the higher intensity on the linewidth is reduced because the intensity broadening rate decreases with buffer-gas pressure.

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Potential for improving the Rubidium Frequency Standard with a novel optical pumping scheme using diode lasers

Cited by 15 publications

References 20 publications

Picotesla magnetometry with coherent dark states

Picotesla magnetometry with coherent dark states

Light-shift suppression in laser optically pumped vapour-cell atomic frequency standards

Dark-line atomic resonances in submillimeter structures

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