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Proceedings Paper

Calcium optical frequency standard
Author(s): Fritz Riehle; Harald Schnatz; Burghard Lipphardt; Uwe Sterr; Tomas Binnewies; Guido Wilpers; Tilmann Trebst; Juergen Helmcke
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Paper Abstract

A laser that is frequency stabilized to the intercombination transition at (lambda) equals 657 nm of laser cooled 40Ca atoms by means of time-domain atom interferences has been developed at PTB. The relative uncertainty of this optical frequency standard is 2.5 X 10-13 and the frequency of the laser has been measured with both, a conventional frequency measurement chain and a femtosecond laser. To reduce the uncertainty of this standard the dependence of its frequency on various parameters was investigated by using phase sensitive and frequency sensitive atom interferometers. Upper bounds were derived for various contributions to the uncertainty as e.g. the influence of gravitational acceleration, collisions of the ballistic atoms, or curvature of the wave fronts of the interrogating laser beams. Further reduction of the uncertainty of the standard is expected from the application of sub-Doppler cooling techniques. A method was devised based on the narrow intercombination transition that enabled us to reduce the velocity spread of the Ca atoms in one dimension close to the recoil limit. The method uses the repeated selection and accumulation of slow atoms from the pre-cooled atomic cloud and the repeated rethermalization of the remaining atoms and results in an increased visibility of the interference structure.

Paper Details

Date Published: 3 May 2001
PDF: 11 pages
Proc. SPIE 4269, Laser Frequency Stabilization, Standards, Measurement, and Applications, (3 May 2001); doi: 10.1117/12.424460
Show Author Affiliations
Fritz Riehle, Physikalisch-Technische Bundesanstalt (Germany)
Harald Schnatz, Physikalisch-Technische Bundesanstalt (Germany)
Burghard Lipphardt, Physikalisch-Technische Bundesanstalt (Germany)
Uwe Sterr, Physikalisch-Technische Bundesanstalt (Germany)
Tomas Binnewies, Physikalisch-Technische Bundesanstalt (Germany)
Guido Wilpers, Physikalisch-Technische Bundesanstalt (Germany)
Tilmann Trebst, Physikalisch-Technische Bundesanstalt (Germany)
Juergen Helmcke, Physikalisch-Technische Bundesanstalt (Germany)

Published in SPIE Proceedings Vol. 4269:
Laser Frequency Stabilization, Standards, Measurement, and Applications
John L. Hall; Jun Ye, Editor(s)

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