Optical reference frequencies are provided by lasers of which the frequencies are stabilized to suitable absorption lines. Presently, twelve reference frequencies/wavelengths within the wavelengths range from 243 nm to 10.3 micrometers are recommended by the International Committee of Weights and Measures as references for the realization of the meter and scientific applications. As typical examples, we describe a diode-pumped, frequency doubled YAG-laser stabilized to an absorption line of molecular iodine and a Ca-stabilized laser. The latter one has been developed in two versions, a transportable system utilizing a small beam of thermal Ca atoms and a stationary standard based on laser cooled and trapped Ca atoms. The frequency of the Ca standard based on cold Ca atoms has been measured by a frequency chain allowing a phase-coherent comparison against the primary standard of time and frequency, the caesium clock. Its value is v_Ca equals 455 986 240 494.13 kHz with a relative standard uncertainty of 2.5 (DOT) 10^-13.

Date Published: 7 May 1999
PDF: 12 pages
Proc. SPIE 3571, Tenth International School on Quantum Electronics: Laser Physics and Applications, (7 May 1999);

Published in SPIE Proceedings Vol. 3571:
Tenth International School on Quantum Electronics: Laser Physics and Applications
Peter A. Atanasov; Dimitar V. Stoyanov, Editor(s)