Since the 90’s, photonics has been at the heart of the time and frequency metrology advancements. Especially laser cooling of atoms has made possible atomic optical clocks and optical frequency combs have imposed themselves as unparalleled measurement tools.

Thanks to those technological advances, frequency and time can now be defined with a nearly 10^-18 accuracy, meaning that an optical atomic clock created at the time of the bigbang would be today accurate within 1 second.