Photonic-Chip Supercontinuum with Tailored Spectra for Counting Optical Frequencies

Optical clocks combined with frequency combs are the future of precision timekeeping, as well as a key enabling technology for applications in communication, navigation, relativistic geodesy, quantum physics, and fundamental measurements. Using a silicon nitride waveguide to spectrally broaden a telecom-frequency comb, the authors perform an optical-clock comparison. Additionally, they present measurements and analysis to support an ``all-in-one'' waveguide design for a next-generation clock network. Such devices will be very useful not just in metrology labs, but also in the field---including space missions.