Phase Coherent Link of an Atomic Clock to a Self-Referenced Microresonator Frequency Comb
The counting and control of optical cycles of light has become common with modelocked laser frequency combs. But even with advances in laser technology, modelocked laser combs remain bulk-component devices that are hand-assembled. In contrast, a frequency comb based on the Kerr-nonlinearity in a dielectric microresonator will enable frequency comb functionality in a micro-fabricated and chip-integrated package suitable for use in a wide-range of environments. Such an advance will significantly impact fields ranging from spectroscopy and trace gas sensing, to astronomy, communications, atomic time keeping and photonic data processing. Yet in spite of the remarkable progress shown over the past years, microresonator frequency combs ("microcombs") have still been without the key function of direct f-2f self-referencing and phase-coherent frequency control that will be critical for enabling their full potential. Here we realize these missing elements using a low-noise 16.4 GHz silicon chip microcomb that is coherently broadened from its initial 1550 nm wavelength and subsequently f-2f self-referenced and phase-stabilized to an atomic clock. With this advance, we not only realize the highest repetition rate octave-span frequency comb ever achieved, but we highlight the low-noise microcomb properties that support highest atomic clock limited frequency stability.
Additional InformationThis work is supported by NIST, NPL, Caltech, the DARPA QuASAR program, the AFOSR and NASA. PD thanks the Humboldt Foundation for support. DCC acknowledges support from the NSF GRFP under Grant No. DGE 1144083. Author contributions: PD, SBP and SAD conceived the experiments. PD and AC designed and performed the experiments. TF contributed to the f_(ceo) stabilization. KB and DCC contributed to the nonlinear spectral broadening. KYY, HL, and KJV provided the microresonator. PD and SAD prepared the manuscript with input from all co-authors.
Submitted - 1511.08103.pdf