INTERCOMPARISON OF NORTHERN EUROPEAN I-127(2)-STABILIZED HE-NE LASERS AT LAMBDA = 633 NM

An international comparison of I-127(2) He-Ne stabilized lasers, used as length standards, has been made. Five laboratories from Sweden, Denmark (two laboratories), Finland and Germany were represented. In addition, two lasers from the Bureau International des Poids et Mesures took part in order to relate the results to earlier comparisons. The reproducibility of the frequency mean of the four components d, e, f and g in the transition R(127)11-5 in iodine 127 for the different lasers was found to be 15 kHz, taken as the standard deviation of the distribution of frequency among the group of ten lasers. Using laser BIPM4 as reference the frequency average of the group of lasers was +3,6 kHz, making this a good reference laser for the current ensemble. Measurements of frequency dependence on modulation amplitude, iodine pressure and, for some lasers, intracavity power are reported. The relative frequency partition of the four components d, e, f and g of each laser was also determined and shown to exhibit characteristics which are new for this type of stabilized laser.