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Evaluating the performance of the NPL femtosecond frequency combs: agreement at the 10 -21 level.

Johnson, L A M; Gill, P; Margolis, H S (2015) Evaluating the performance of the NPL femtosecond frequency combs: agreement at the 10 -21 level. Metrologia, 52 (1). pp. 62-71.

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Abstract

Results are presented from a series of comparisons between two independent femtosecond frequency comb systems at NPL, which were carried out in order to assess their systematic uncertainty. Simultaneous measurements with the two systems demonstrate agreement at the level of 5 × 10^-18 when measuring an optical frequency against a common microwave reference. When simultaneously measuring the ratio of two optical frequencies, agreement at the 3 × 10^-21 level is observed. The results represent the highest reported level of agreement to date between Ti:Sapphire and Er-doped femtosecond combs. The limitations of the combs when operating in these two different manners are discussed, including traceability to the SI second, which can be achieved with an uncertainty below 1 × 10^-16. The technical details presented underpin recent absolute frequency measurements of the 88Sr+ and 171Yb+ optical clock transitions at NPL, as well as a frequency ratio measurement between the two optical clock transitions in 171Yb+.

Item Type: Article
Subjects: Time and Frequency
Time and Frequency > Optical Frequency Standards and Metrology
Identification number/DOI: 10.1088/0026-1394/52/1/62
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6480

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