A quarter-century of optical frequency combs (Keynote Presentation)

Introduced about 25 years ago, the optical frequency comb has made routine the counting and synthesis of the oscillations of light on the femtosecond time scale. As such, it is an essential component of all optical clocks and time-transfer systems with precision at the 18th digit. The coherent microwave-to-optical capabilities of frequency combs extend to wide-ranging applications in fundamental and applied spectroscopy, the synthesis of microwaves with ultra-low phase noise, and the discovery of planets orbiting distant stars. In practically all these cases, optical frequency combs have been employed as classical sources of laser light. Here, a new avenue of research involves the development of squeezed optical frequency combs, and the use of such quantum combs for enhanced metrology. This talk will provide an overview of the state-of-the-art of both classical and quantum frequency combs and highlight their use in the most impactful applications.