https://nrc-publications.canada.ca/fra/voir/objet/?id=41b3a8b1-9f6c-4100-8f60-8141b5a16604
Absolute frequency measurement of a laser at 1556 nm locked to the 5S1/2 - 5D5/2 two-photon...
Absolute frequency measurement of a laser at 1556 nm locked to the 5S1/2 - 5D5/2 two-photon transition in 87-Rb