INTERNATIONAL COMPARISON OF IODINE-STABILIZED HELIUM-NEON LASERS AT LAMBDA=633NM INVOLVING 7 LABORATORIES

An international comparison has been made of the frequencies of stabilized He-Ne lasers using intracavity saturated absorption of I-127(2) at lambda = 633 nm in Bratislava (Czechoslovakia). This comparison, organized by the CSMU (Bratislava), involved at the same time seven laboratories from five countries: the ASMW (German Democratic Republic), the CSMU (Bratislava, Czechoslovakia), the CSMU (Praha, Czechoslovakia), the CSAV (Brno, Czechoslovakia), the OMH (Hungary), the VNIIM (USSR) and the BIPM. The range of the frequency differences between all the lasers and the two BIPM travelling lasers was from - 15,9 kHz to 8,8 kHz, with a mean of DELTA-f = - 3,3 kHz and an estimated standard deviation of 8,5 kHz (4,7 kHz corresponds to 1 part in 10(11), in relative terms). Using the measurements carried out at the BIPM before and after this comparison between the travelling lasers BIPM4 and BIPM10 and the stationnary reference laser BIPM2, we can link our results to previous international comparisons involving the BIPM. Taking into account the values of these measurements, the mean frequency difference becomes: DELTA-f = - [1,6 +/- 8,2] kHz.