All-optical frequency division on-chip using a single laser

Ultralow-noise microwave sources are essential for advanced timekeeping, radar, and communication systems. Optical frequency division (OFD), the most effective technique for generating low-noise microwaves, traditionally relies on complex and bulky optical and electronic setups. We demonstrate an all-optical OFD approach that requires only a single pump laser, a compact photonic chip, and simple electronic driver circuits. The photonic chip comprises two high-Q microresonators: one generates an optical-parametric oscillator (OPO) as a two-point reference for OFD, while the other produces a Kerr comb as the OFD clockwork. A coupling waveguide synchronizes the two resonators, enabling the conversion of the OPO’s low-noise beat note (~8 THz) into the microwave regime without introducing additional noise. We demonstrate OFD at 227 GHz and 16 GHz by adjusting the cavity length, yielding a noise level at 10-kHz offset frequency of -87 dBc/Hz and -124 dBc/Hz, respectively. Finally, we introduce novel techniques to significantly suppress key OPO noise sources, including thermorefractive and vacuum noise.