International Comparison of He-Le Lasers Stabilized on the Saturated Absorption of 127 Iodine at λ = 633 nm

From June 18 to 24, 1979 at VNIIM comparisons were made of He-Ne/ 127 I 2 lasers belonging to VNIIM* and BIPM. Frequency separations of the hyperfine components d, e, f, g of the R(127) line of iodine were measured and investigations carried out of the influence of amplitude modulation and the pressure of iodine, and of the power shifts. The frequency separations of d, e, f, g components were also measured for the VNIIM stabilized laser, using a BIPM servo loop. Lasers VNIIM7, VNIIM1, BIPM3 and BIPM6 were used. This comparison was interesting because the optical and mechanical designs, iodine cells and laser tubes were completely different. It is the second comparison between VNIIM and BIPM. It is also a part of a series of international comparisons between national laboratories and BIPM aimed at improving the coherence of laser wavelength and frequency measurements throughout the world. VNIIM lasers have the following parameters: the distance between the mirrors is 31 cm; the flat mirror, which is located near the iodine cell, has a reflectivity of 99 percent; the other one has a radius of curvature of 1.2 m and a maximum reflectivity.