Ultrafast mode-locked frequency microcombs: fundamentals and precision metrology (Conference Presentation)

In this talk, first, we describe chip-scale coherent mode-locking in microresonator frequency combs, verified by interferometric femtosecond timing jitter measurements and phase-resolved ultrafast spectroscopy. Normal dispersion sub-100-fs mode-locking is also observed, supporting by nonlinear modeling and analytics. Second we describe the noise limits in full microcomb stabilization, locking down both repetition rate and one comb line against a reference. Active stabilization improves the long-term stability to an instrument-limited residual instability of 3.6 mHz per root tau and a tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7×10−16. Third we describe graphene-silicon nitride hybrid microresonators for tunable frequency modes, variants of soliton mode-locked states and crystals, and controllable Cerenkov radiation. Our studies provide a platform towards precision spectroscopy, frequency metrology, timing clocks, and coherent communications.