Optical frequency combs for atomic clocks and continental frequency dissemination

LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, 61 Avenue de l’Observatoire, F-75014, Paris, France

^* e-mail: Rodolphe.LeTargat@obspm.fr

Abstract

Nearly 25 years ago, Optical Frequency Combs (OFCs) have revolutionized practically from one day to the next the metrology of optical frequencies. Before that, only a few labs in the world could connect the optical (~10¹⁵ Hz) and the microwave (~10¹⁰ Hz) domains, at the price of the complex operation of a chain of multiple non-linear frequency conversions. In contrast, OFCs provided a tabletop instrument, compact, reliable and operable by a single scientist. Unmistakeable sign: only a few years had passed before pioneering inventors of OFCs Theodor Hänsch and John Hall were awarded the 2005 Nobel prize in Physics, together with Roy Glauber.