Bridging ultrahigh-Q devices and photonic circuits

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Optical microresonators are essential to a broad range of technologies and scientific disciplines. However, many of their applications rely on discrete devices to attain challenging combinations of ultra-low-loss performance (ultrahigh Q) and resonator design requirements. This prevents access to scalable fabrication methods for photonic integration and lithographic feature control. Indeed, finding a microfabrication bridge that connects ultrahigh-Q device functions with photonic circuits is a priority of the microcavity field. Here, an integrated resonator having a record Q factor over 200 million is presented. Its ultra-low-loss and flexible cavity design brings performance to integrated systems that has been the exclusive domain of discrete silica and crystalline microcavity devices. Two distinctly different devices are demonstrated: soliton sources with electronic repetition rates and high-coherence/low-threshold Brillouin lasers. This multi-device capability and performance from a single integrated cavity platform represents a critical advance for future photonic circuits and systems.

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We thank O. Painter and B. Baker for assistance with the PECVD silicon nitride process, H. Atwater and W.-H. Cheng for assistance with silica atomic layer deposition, M. Hunt for assistance with electron-beam microscopy, Y.-H. Lai for technical assistance, and A. Matsko and J. Bowers for helpful discussions. We also gratefully acknowledge the Defense Advanced Research Projects Agency under the DODOS (award no. HR0011-15-C-0055, sub award KK1540) and PRIGM:AIMS (grant no. N66001-16-1-4046) programs and the Kavli Nanoscience Institute.

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Author notes

  1. These authors contributed equally: Ki Youl Yang, Dong Yoon Oh and Seung Hoon Lee.


  1. T. J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA, USA

    • Ki Youl Yang
    • , Dong Yoon Oh
    • , Seung Hoon Lee
    • , Qi-Fan Yang
    • , Xu Yi
    • , Boqiang Shen
    • , Heming Wang
    •  & Kerry Vahala


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K.Y.Y., D.Y.O., S.H.L. and K.V. conceived the fabrication process and resonator design. K.Y.Y., D.Y.O. and S.H.L. fabricated and tested the resonator structures with assistance from B.S. and H.W. K.Y.Y., D.Y.O., S.H.L., Q.F.Y., X.Y., B.S. and H.W. conducted soliton and Brillouin laser measurements. All authors analysed the data and contributed to writing the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Kerry Vahala.

Supplementary information

  1. Supplementary Information

    This file describes the intrinsic cavity Q measured from 1,520–1,560 nm, investigation of cavity loss mechanism, waveguide–resonator coupling, the high-temperature annealing effect on cavity Q, and mode filtering.