Frequency combs applications and optical frequency standards

A laser frequency comb allows the conversion of the very rapid oscillations of visible light of some 100's of THz down to frequencies that can be handled with conventional electronics, say below 100 GHz. This capability has enabled the most precise laser spectroscopy experiments yet that allowed to test quantum electrodynamics, to determine fundamental constants and to search for possible slow changes of these constants. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks, that are about to outperform the current cesium atomic clocks. © Società Italiana di Fisica.