The ratio of an unknown laser wavelength to that of a standard is quickly determined by a two-beam interferometer with a corner-cube reflector moving on an air track. Standard and unknown wavelength beams travel identical paths in opposite directions, so refractive index corrections are minimized. Accuracy is about six parts in 10<sup>8</sup>. Absolute measurements of some iodine hyperfine component wavelengths are reported.
© 1976 Optical Society of America
F. V. Kowalski, R. T. Hawkins, and A. L. Schawlow, "Digital wavemeter for cw lasers," J. Opt. Soc. Am. 66, 965-966 (1976)