The I2-stabilized Ar/+/ laser at a wavelength of 515 nm /nu equals 582 THz/

Various methods to control the frequency of gas lasers by an iodine absorption signal are described. A simple stabilization method is developed for the case of the Ar(+) laser using a Doppler broadened absorption signal, making the stabilized laser frequency reproducible to about 4 x 10 to the -9th nu. The laser frequency can be referred to a single I2 hyperfine component with Doppler-free methods, and using internal I2 cells, the laser frequency is reproducible from 2 x 10 to the -10th to 4 x 10 to the -11th nu. With an external I2 cell, the frequency of the laser is reproducible to 3 x 10 to the -12th nu. It is shown that laser radiation at lambda(a3) equals 514.673467 nm represents an extremely reproducible fixed point of the wavelength or frequency scale in the visible part of the spectrum.