FREQUENCY COMPARISON OF HE-NE IODINE LASERS AT LAMBDA=633 NM BETWEEN THE NILPRP AND THE ISI, AND TRACEABILITY THROUGH THE BIPM/

We report the results of a bilateral laser frequency comparison betwee n lasers from the National Institute for Laser, Plasma and Radiation P hysics (NILPRP, Romania: laser RO2) and the Institute of Scientific In struments (ISI, Czech Republic: laser INV3). The main objective was to correlate the results obtained from these two laboratories and the pr evious results obtained by each of these laboratories against the Bure au International des Poids et Mesures (BIPM: lasers BIPM4 and BIPMP3). The result of a set of ten direct measurements showed a medium freque ncy difference of Delta f(corr) = f(RO2) - f(INV3) = -15,1 kHz, With a n estimated standard uncertainty (1 sigma) of s = 2,6 kHz, compared wi th the expected mean value, resulting from earlier comparisons, of Del ta f(corr) = f(RO2) - f(INV3) = -10,7 kHz with s = 7,4 kHz. Once corre ctions were applied, the standard uncertainty (repeatability) of the f requency measurements improved from 6,0 kHz to 2,6 kHz.