The CCL-K11 ongoing key comparison. Final report for 2023

Six lasers from six national metrological institutes (NMIs) were compared in the year 2023 as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comité Consultative des Longueurs (CCL) in 2007. The absolute frequency of theses lasers was measured in three different node laboratories following the technical protocol for CCL-K11. All are practical realisations of the definition of the metre according to the MeP for the definition of the metre. Five standards are He-Ne-lasers stabilized on the f component of the R(127) 11-5 transitions of molecular iodine 127I2 with a wavelength of approximately 633 nm. The sixth standard is a fibre laser stabilized to the P(16) (ν1+ν3) transition of molecular acetylene 13C2H2 with a wavelength of approximately 1542 nm. The technical protocol was deliberately designed to accommodate artefacts of different wavelengths in a common framework. The results of these measurements are compiled in the present report. The comparison reports, as communicated by each participant, are included in the main document. This document constitutes the thirteenth final report for the ongoing key comparison CCL-K11. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).