Intercomparison of Optical Frequencies at 473 THz of ¹²⁷I₂-stabilized He-Ne Lasers from the Swedish National Testing and Research Institute and the Bureau International des Poids et Mesures

An account is given of an intercomparison of the optical frequencies of I2-stabilized He-Ne lasers at 473 THz (633 nm) performed at the Bureau International des Poids et Mesures (BIPM), Sevres, France during June 12-16, 1989. The lasers, SP1 and BIPM2, belong to SP, Boras, Sweden and BIPM, respectively. It was found in a matrix of frequency difference measurements that laser SP1 differed in optical frequency from laser BIPM2 by + 8,0 kHz, with a standard deviation of 1,6 kHz and at a one-way intracavity power of 23,7 mW for laser SP1 and 8,3 mW for laser BIPM2. The reproducibility of the laser SP1 frequency was estimated to be +/- 20 kHz.