International comparison of He-Ne lasers stabilized with¹²⁷I₂at     633 nm between the SMU (Slovakia) and the BEV (Austria)

Abstract

The comparison of two lasers from the Slovak Institute of Metrology (SMU, Slovakia) and one laser from the Bundesamt für Eich-und Vermessungswesen (BEV, Austria) in March 2000 followed that undertaken by the Bureau International des Poids et Mesures (BIPM) at the BEV in September 1999. These two comparisons were indirectly linked through the frequency of the BEV2 laser. As a first step, two SMU lasers (SMU-B2 and SMU-B3) were compared with BEV2 (in this case the reference laser) and then the SMU lasers were mutually compared, with the parameters of all three lasers set up as they are normally used. Uncorrected frequency differences with respect to BEV2 were -15.2 kHz (SMU-B2) and +19.7 kHz (SMU-B3), i.e. within the expanded uncertainty of 2 24 kHz (5 10 -11 ) recommended by the International Committee for Weights and Measures (CIPM). Taking into account the correction to the recommended values of the parameters, these differences were reduced to -5.1 kHz and +4.6 kHz, respectively. After transfer to the BIPM reference laser, the differences of the SMU lasers were -7.4 kHz and +2.3 kHz, respectively, i.e. within the range of 1 12 kHz (2.5 10 -11 ) recommended by the CIPM for laser parameters meeting the recommended values. The best frequency stabilities, expressed as relative Allan standard deviations, were 8.0 10 -12 , 2.6 10 -12 and 9.2 10 -13 for sampling times of 10 s, 100 s and 1000 s, respectively. The overall best value was 6.0 10 -13 for a sampling time of 2500 s.