A precision long-arm scanning Michelson interferometer system is described that is capable of measuring absolute laser wavelength to within several parts in 109 in the 10-µm spectral range and to within several parts in 1011 in the visible range. The R(14) line of the CO2 9.4-µm band is measured to be 9.305 385 613 (70) µm. This measured value and the known frequency of this line give a value for the speed of light: c = 299 792 457.6 (2.2) m/sec, in agreement with the recent independent measurements of c and its recommended value.
J.-P. Monchalin, M. J. Kelly, J. E. Thomas, N. A. Kurnit, A. Szöke, A. Javan, F. Zernike, and P. H. Lee, "Determination of the speed of light by absolute wavelength measurement of the R(14) line of the CO2 9.4-µm band and the known frequency of this line," Opt. Lett. 1, 5-7 (1977)