Low-noise microwave generation from micro-combs via transferring the timing stability of mode-locked lasers

We stabilized the timing of a 9.92-GHz microcomb using a 250-MHz mode-locked laser as a reference. To ensure precise timing linkage between two optical pulse sources, the electro-optic sampling-based timing detector (EOS-TD), which can detect the timing difference between microwave and optical pulse train with attoseconds precision, was employed. The 9.92-GHz microwave phase noise of the micro-comb was suppressed to –100 dBc/Hz at 10 kHz offset frequency, which is suppressed by >25 dB compared to the free-running case.