RECENT ACTIVITIES AT BIPM IN THE FIELD OF STABILIZED LASERS - RADIATIONS RECOMMENDED FOR THE DEFINITION OF THE METER

The results of international comparisons of iodine stabilized He-Ne lasers at lambda = 633 nm between the Bureau International des Poids et Mesures (BIPM) and eleven national laboratories are presented. The measured frequency differences are all inside +/- 3 parts in 10(11). New investigations concerning the He-Ne lasers at lambda = 612 nm using internal or external iodine cells are discussed. The frequency reproducibility is limited by, among other things, the quality of the iodine cells. Therefore the contamination of iodine cells has been studied using laser-induced fluorescence. First results obtained on the green line of He-Ne at lambda = 543 nm stabilized on iodine are also presented. The frequency difference between two such systems was found to be 14 kHz with a repeatability of 5 kHz.