Dispersive-wave-agile optical frequency division

The remarkable frequency stability of resonant systems in the optical domain (optical cavities and atomic transitions) can be harnessed at frequency scales accessible by electronics using optical frequency division. This capability is revolutionizing technologies spanning time keeping to high-performance electrical signal sources. A version of the technique called two-point optical frequency division (2P-OFD) is proving advantageous for application to high-performance signal sources. In 2P-OFD, an optical cavity anchors two spectral endpoints defined by lines of a frequency comb. The comb need not be self-referenced, which greatly simplifies the system architecture and reduces power requirements. Here, a 2P-OFD microwave signal source is demonstrated with record-low phase noise using a microcomb. Key to this advance is a spectral endpoint defined by a frequency-agile single-mode dispersive wave that is emitted by the microcomb soliton. Moreover, the system frequency reference is a compact all-solid-state optical cavity with a record Q factor. A hybridly packaged version of the system offers excellent longer term stability. The results advance integrable microcomb-based signal sources into the performance realm of much larger microwave sources. Using two-point optical frequency division based on a frequency-agile single-mode dispersive wave, a microwave signal source with record-low phase noise using a microcomb is demonstrated, offering over tenfold lower phase noise than state-of-the-art approaches.