FREQUENCY COMPARISON OF IODINE-STABILIZED HE-NE LASERS AT 633 NM FROMTHE IMGC AND THE IFA-IFTAR

The results of an international comparison between the He-Ne lasers st abilized to I-127(2) at 633 nm of the IMGC (Istituto di Metrologia ''G . Colonnetti'', Turin, Italy) and the IFA-IFTAR (Institute of Atomic P hysics-IFTAR, Department of Lasers, Bucharest, Romania) are reported. The mean frequency difference, considering the hyperfine structure com ponents d, e, f and g of the R(127)11-5 transition, was Delta nu = nu( RO.2) - nu(IMGC4/5)=3,8 kHz, standard uncertainty u=5,7 kHz, or Delta nu/nu(0)=0,8 x 10(-11), standard uncertainty u=1,2 x 10(-11). The freq uency stability, expressed as the relative Allan standard deviation of the beat note between the two lasers, resulted 3,7 x 10(-12) for a 10 0 s sampling time.