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Microcavity Kerr optical frequency division with integrated SiN photonics

Nature Photonics volume 19, pages 637–642 (2025)Cite this article

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Abstract

Optical frequency division has revolutionized microwave and millimetre-wave generation and set spectral purity records owing to its unique capability to transfer high fractional stability from optical to electronic frequencies. Recently, rapid developments in integrated optical reference cavities and microresonator-based optical frequency combs (microcombs) have created a path to transform optical frequency division technology to the chip scale. Here we demonstrate an ultralow-phase-noise millimetre-wave oscillator by leveraging integrated photonic components and microcavity Kerr optical frequency division. The oscillator derives its stability from an integrated complementary-metal–oxide–semiconductor-compatible SiN coil cavity, and the optical frequency division is achieved spontaneously through Kerr interaction in the integrated SiN microresonator between the soliton microcombs and the injected reference lasers. Besides achieving low phase noise for integrated millimetre-wave oscillators, our demonstration greatly simplifies the implementation of integrated optical frequency division oscillators and could be useful in applications of radar, spectroscopy and astronomy.

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Fig. 1: Concept of Kerr OFD for stable microwave and mmWave generation.
Fig. 2: Experimental setup.
Fig. 3: Observation of Kerr locking and Kerr OFD.
Fig. 4: Characterization of mmWave generated from Kerr OFD.
Fig. 5: Approximate phase noise of several integrated microcomb-based microwave and mmWave oscillators.

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Data availability

Data for Figs. 3–5 and Extended Data Fig. 1 are available via Figshare at https://doi.org/10.6084/m9.figshare.27629772 (ref. 43).

Code availability

The codes that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We acknowledge M. Woodson and S. Estrella from Freedom Photonics for the MUTC PD fabrication, Ligentec for SiN microresonator fabrication and Q.-X. Ji at the California Institute of Technology for helpful discussion. We also acknowledge DARPA GRYPHON (HR0011-22-2-0008, all authors), National Science Foundation (2023775; S.S., F.T., S.H., B.W., Z.Y., R.L., J.S.M., S.M.B., A.B. and X.Y.) and the Air Force Office of Scientific Research (FA9550-21-1-0301; S.S., B.W., Z.Y., R.L. and X.Y.). The views and conclusions contained in this document are those of the authors and should not be interpreted as representing official policies of DARPA, ARPA-E or the US Government.

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Author notes

  1. Shuman Sun

    Present address: T.J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA, USA

Authors and Affiliations

  1. Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, USA

    Shuman Sun, Fatemehsadat Tabatabaei, Samin Hanifi, Beichen Wang, Zijiao Yang, Ruxuan Liu, Jesse S. Morgan, Steven M. Bowers, Andreas Beling & Xu Yi

  2. Department of Electrical and Computer Engineering, University of California Santa Barbara, Santa Barbara, CA, USA

    Mark W. Harrington, Kaikai Liu, Jiawei Wang & Daniel J. Blumenthal

  3. Department of Physics, University of Virginia, Charlottesville, VA, USA

    Zijiao Yang & Xu Yi

  4. Infleqtion, Louisville, CO, USA

    Paul A. Morton

  5. Honeywell Aerospace Technologies, Plymouth, MN, USA

    Karl D. Nelson

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Contributions

X.Y. and S.S. designed the experiments. S.S., F.T. and S.H. performed the system measurements. M.W.H., K.L., J.W., D.J.B., K.D.N. and P.A.M. developed the reference lasers. J.S.M. and A.B. designed and fabricated the CC-MUTC PDs. S.S., X.Y., F.T. and S.H. analysed the experimental results. X.Y., D.J.B., A.B., S.M.B., P.A.M. and K.D.N. supervised and led the scientific collaboration. All authors participated in preparing the manuscript.

Corresponding authors

Correspondence to Daniel J. Blumenthal or Xu Yi.

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Nature Photonics thanks David Moss and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Phase noise comparison in different OFD systems.

(a) Phase noise comparison of reference lasers used in ref. 13 and in this work. While the length of the coil reference cavities is both 4 meters, the quality factor of the cavity in this work is improved, and the reference cavity is now packaged to isolate environmental noises. The reference laser in this work reaches the thermal refractive noise limit between 1 kHz to 10 kHz offset frequency. (b) Phase noise comparison of conventional OFD13 versus the Kerr OFD in this work. The same reference lasers and soliton microcomb are used for both OFD oscillators. The conventional OFD in our setup has a servo bandwidth around 150 kHz, and the in-loop noise is limiting phase noise starting around 10 kHz offset frequency. In the low offset frequency, both methods give similar phase noise results. The phase noise in both panel (a) and (b) are measured by using optical interferometry method.

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Sun, S., Harrington, M.W., Tabatabaei, F. et al. Microcavity Kerr optical frequency division with integrated SiN photonics. Nat. Photon. 19, 637–642 (2025). https://doi.org/10.1038/s41566-025-01668-3

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