Abstract
Five frequency stabilized laser types were recommended as the optical frequency / wavelength standards for the practical realization of the meter which was redefined in 1983. Since 1983, work in national laboratories, Bureau International des Poids et Mesures and elsewhere has substantially improved the reproducibility of the radiations which are suitable for the practical realization of the meter. In addition, science and technology demand improved accuracy in the realization of the meter. In the present situation, Comite International des Poids et Mesures should be replaced by the new list of recommended radiations in this September. This article has reviewed frequencies and wavelengths of the list for a new recommendation which was discussed in a working group of Comite Consultatif pour la Definition du Metre in 1992. A research trend of frequency stabilization for semiconductor lasers and solid state lasers is also covered. Furthermore frequency stability, accuracy and reproducibility of the stabilized lasers required as the optical frequency / wavelength standards are described. In particular, spectral broadening due to pressure, power and transit time, and residual broadening are discussed in detail, using an example, the saturated absorption spectrum of methane at 3.39 μm.
