An all-optical microwave frequency standard based on coherent population trapping (CPT) in is developed. The CPT resonances are detected by an ordinary edge-emitting diode laser in a simple optical setup. A buffer-gas mixture is carefully optimized to yield a narrow linewidth and a reduced temperature dependence of the resonance frequency. With the developed system we are able to measure ultranarrow optically induced hyperfine CPT resonances at <20 Hz, which is in good agreement with the linewidth calculated from experimental parameters. The frequency of an RF-signal generator has been stabilized to the CPT resonance between the two magnetic sublevels. The relative frequency stability (square root of Allan variance) follows a slope of The best stability of is reached at an integration time of This stability is sufficient for many high-precision applications. Frequency-shift measurements were made to evaluate the frequency dependencies on the operation parameters.
© 2003 Optical Society of AmericaFull Article | PDF Article
Svenja Knappe, Leo Hollberg, and John Kitching
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David F. Phillips, Irina Novikova, Christine Y.-T. Wang, Ronald L. Walsworth, and Michael Crescimanno
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S. Knappe, P.D.D. Schwindt, V. Shah, L. Hollberg, J. Kitching, L. Liew, and J. Moreland
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