Abstract
Laser has been keeping a close relation with atomic frequency standards since its origin. Recently, progress in the laser and the optical technology brought a lot of new developments in the atomic frequency standards in both microwave region and optical region. Especially, new technology on optical frequency measurements, laser stabilization and atom control technique are now opening a way to new standards in optical region whose accuracies can be beyond the limit of Cs standards. In this article we show the basics of the characterization of frequency and introduce an outline of the recent progress in atomic frequency standards and laser technology.
