Wavelength ratio of stabilized laser radiation at 339 μm and 0633 μm

A servo controlled Michelson interferometer with a displacement of 3.8 m between the final positions of the movable mirror has been developed for precise laser wavelength comparisons. This instrument has been used to determine the wavelength ratio between the radiation of a 3.39-μm He–Ne laser stabilized to the CH4 transition ν3, P(7), component F2(2) and that of a 633-nm He–Ne laser stabilized to the 127I2 transition 11–5, R(127), component i. Expanded laser beams of Gaussian structure were used and the diffraction correction for the infrared beam was determined from measured beam parameters. Two series of measurements were carried out, approximating measurements with the total cross section and with only the central part of the beam. The results confirm the expected change of the diffraction correction. The weighted mean value of both measurement series yields λCH4/λI2 = 5.359 048 1743 (1 ± 3 × 10−10).