Optical-frequency synthesizers, which generate frequency-stable light from a single microwave-frequency reference, are revolutionizing ultrafast science and metrology, but their size, power requirement and cost need to be reduced if they are to be more widely used. Integrated-photonics microchips can be used in high-coherence applications, such as data transmission1, highly optimized physical sensors2 and harnessing quantum states3, to lower cost and increase efficiency and portability. Here we describe a method for synthesizing the absolute frequency of a lightwave signal, using integrated photonics to create a phase-coherent microwave-to-optical link. We use a heterogeneously integrated III–V/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon chips and pumped by off-chip lasers. The laser frequency output of our optical-frequency synthesizer can be programmed by a microwave clock across 4 terahertz near 1,550 nanometres (the telecommunications C-band) with 1 hertz resolution. Our measurements verify that the output of the synthesizer is exceptionally stable across this region (synthesis error of 7.7 × 10−15 or below). Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here. Leveraging high-volume semiconductor processing built around advanced materials could allow such low-cost, low-power and compact integrated-photonics devices to be widely used.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


  1. 1.

    Rumley, S. et al. Silicon photonics for exascale systems. J. Lightwave Technol. 33, 547–562 (2015).

  2. 2.

    Purdy, T. P., Grutter, K. E., Srinivasan, K. & Taylor, J. M. Quantum correlations from a room-temperature optomechanical cavity. Science 356, 1265–1268 (2017).

  3. 3.

    O’Brien, J. L., Furusawa, A. & Vučković, J. Photonic quantum technologies. Nat. Photonics 3, 687–695 (2009).

  4. 4.

    Hall, J. L. Nobel Lecture: Defining and measuring optical frequencies. Rev. Mod. Phys. 78, 1279–1295 (2006).

  5. 5.

    Hänsch, T. W. Nobel Lecture: Passion for precision. Rev. Mod. Phys. 78, 1297–1309 (2006).

  6. 6.

    Jost, J. D., Hall, J. L. & Ye, J. Continuously tunable, precise, single frequency optical signal generator. Opt. Express 10, 515–520 (2002).

  7. 7.

    Giorgetta, F. R., Coddington, I., Baumann, E., Swann, W. C. & Newbury, N. R. Fast high-resolution spectroscopy of dynamic continuous-wave laser sources. Nat. Photonics 4, 853–857 (2010).

  8. 8.

    Sinclair, L. C. et al. Operation of an optically coherent frequency comb outside the metrology lab. Opt. Express 22, 6996–7006 (2014).

  9. 9.

    Komljenovic, T. et al. Heterogeneous silicon photonic integrated circuits. J. Lightwave Technol. 34, 20–35 (2016).

  10. 10.

    Del’Haye, P. et al. Optical frequency comb generation from a monolithic microresonator. Nature 450, 1214–1217 (2007).

  11. 11.

    Savchenkov, A. A. et al. Tunable optical frequency comb with a crystalline whispering gallery mode resonator. Phys. Rev. Lett. 101, 093902 (2008).

  12. 12.

    Kippenberg, T. J., Holzwarth, R. & Diddams, S. A. Microresonator-based optical frequency combs. Science 332, 555–559 (2011).

  13. 13.

    Moss, D. J., Morandotti, R., Gaeta, A. L. & Lipson, M. New CMOS-compatible platforms based on silicon nitride and Hydex for nonlinear optics. Nat. Photonics 7, 597–607 (2013).

  14. 14.

    Grudinin, I. S., Yu, N. & Maleki, L. Generation of optical frequency combs with a CaF2 resonator. Opt. Lett. 34, 878–880 (2009).

  15. 15.

    Ferdous, F. et al. Spectral line-by-line pulse shaping of on-chip microresonator frequency combs. Nat. Photonics 5, 770–776 (2011).

  16. 16.

    Papp, S. B. & Diddams, S. A. Spectral and temporal characterization of a fused-quartz-microresonator optical frequency comb. Phys. Rev. A 84, 053833 (2011).

  17. 17.

    Li, J., Lee, H., Chen, T. & Vahala, K. J. Low-pump-power, low-phase-noise, and microwave to millimeter-wave repetition rate operation in microcombs. Phys. Rev. Lett. 109, 233901 (2012).

  18. 18.

    Cole, D. C., Lamb, E. S., Del’Haye, P., Diddams, S. A. & Papp, S. B. Soliton crystals in Kerr resonators. Nat. Photonics 11, 671–676 (2017).

  19. 19.

    Okawachi, Y. et al. Bandwidth shaping of microresonator-based frequency combs via dispersion engineering. Opt. Lett. 39, 3535–3538 (2014).

  20. 20.

    Herr, T. et al. Temporal solitons in optical microresonators. Nat. Photonics 8, 145–152 (2014).

  21. 21.

    Leo, F. et al. Temporal cavity solitons in one-dimensional Kerr media as bits in an all-optical buffer. Nat. Photonics 4, 471–476 (2010).

  22. 22.

    Yi, X., Yang, Q.-F., Yang, K. Y., Suh, M.-G. & Vahala, K. Soliton frequency comb at microwave rates in a high-Q silica microresonator. Optica 2, 1078–1085 (2015).

  23. 23.

    Brasch, V. et al. Photonic chip-based optical frequency comb using soliton Cherenkov radiation. Science 351, 357–360 (2016).

  24. 24.

    Li, Q. et al. Stably accessing octave-spanning microresonator frequency combs in the soliton regime. Optica 4, 193–203 (2017).

  25. 25.

    Pfeiffer, M. H. P. et al. Octave-spanning dissipative Kerr soliton frequency combs in Si3N4 microresonators. Optica 4, 684–691 (2017).

  26. 26.

    Jost, J. D. et al. Counting the cycles of light using a self-referenced optical microresonator. Optica 2, 706–711 (2015).

  27. 27.

    Del’Haye, P. et al. Phase-coherent microwave-to-optical link with a self-referenced microcomb. Nat. Photonics 10, 516–520 (2016).

  28. 28.

    Brasch, V., Lucas, E., Jost, J. D., Geiselmann, M. & Kippenberg, T. J. Self-referenced photonic chip soliton Kerr frequency comb. Light Sci. Appl. 6, e16202 (2017).

  29. 29.

    Arafin, S. et al. Power-efficient Kerr frequency comb based tunable optical source. IEEE Photonics J. 9, 6600814 (2017).

  30. 30.

    Arafin, S. et al. Towards chip-scale optical frequency synthesis based on optical heterodyne phase-locked loop. Opt. Express 25, 681–695 (2017).

  31. 31.

    Del’Haye, P., Arcizet, O., Schliesser, A., Holzwarth, R. & Kippenberg, T. J. Full stabilization of a microresonator-based optical frequency comb. Phys. Rev. Lett. 101, 053903–053904 (2008).

  32. 32.

    Papp, S. B. et al. Microresonator frequency comb optical clock. Optica 1, 10–14 (2014).

  33. 33.

    Komljenovic, T. et al. Widely tunable narrow-linewidth monolithically integrated external-cavity semiconductor lasers. IEEE J. Sel. Top. Quantum Electron. 21, 214–222 (2015).

  34. 34.

    Briles, T. C. et al. Kerr-microresonator solitons for accurate carrier-envelope-frequency stabilization. Preprint at https://arxiv.org/abs/1711.06251 (2017).

  35. 35.

    Yang, K. Y. et al. Bridging ultrahigh-Q devices and photonic circuits. Nat. Photonics (2018).

  36. 36.

    Stone, J. et al. Thermal and nonlinear dissipative-soliton dynamics in Kerr microresonator frequency combs. Preprint at https://arxiv.org/abs/1708.08405 (2017).

  37. 37.

    Bluestone, A. et al. Heterodyne-based hybrid controller for wide dynamic range optoelectronic frequency synthesis. Opt. Express 25, 29086–29097 (2017).

  38. 38.

    Ycas, G., Osterman, S. & Diddams, S. A. Generation of a 660–2100 nm laser frequency comb based on an erbium fiber laser. Opt. Lett. 37, 2199–2201 (2012).

  39. 39.

    Greenhall, C. A. & Riley, W. J. in Proc. PTTI 2003, 267–280 (2003).

  40. 40.

    Volet, N. et al. Semiconductor optical amplifiers at 2.0-µm wavelength on silicon. Laser Photonics Rev. 11, 1600165 (2017).

  41. 41.

    Chang, L. et al. Thin film wavelength converters for photonic integrated circuits. Optica 3, 531–535 (2016).

  42. 42.

    Srinivasan, S. et al. Coupled-ring-resonator-mirror-based heterogeneous III–V silicon tunable laser. IEEE Photonics J. 7, 2700908 (2015).

  43. 43.

    Del’Haye, P., Papp, S. B. & Diddams, S. A. Hybrid electro-optically modulated microcombs. Phys. Rev. Lett. 109, 263901 (2012).

Download references


We thank Srico, Inc. for use of the waveguide PPLN device, Aurrion Inc. for use of the III–V/Si tunable laser, and D. Hickstein, T. Dunker, A. Wallin, D. Carlson and Z. Newman for comments on the experiment. N.V. acknowledges support from the Swiss National Science Foundation (SNSF). This research is supported by the Defense Advanced Research Projects Agency DODOS program and NIST. We thank R. Lutwak and the DODOS program management team for discussions throughout the experiment.

Reviewer Information

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

Author information


  1. Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO, USA

    • Daryl T. Spencer
    • , Tara Drake
    • , Travis C. Briles
    • , Jordan Stone
    • , Laura C. Sinclair
    • , Connor Fredrick
    • , Nathan R. Newbury
    • , Scott A. Diddams
    •  & Scott B. Papp
  2. Department of Physics, University of Colorado, Boulder, CO, USA

    • Travis C. Briles
    • , Jordan Stone
    • , Connor Fredrick
    • , Scott A. Diddams
    •  & Scott B. Papp
  3. Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD, USA

    • Qing Li
    • , Daron Westly
    • , B. Robert Ilic
    •  & Kartik Srinivasan
  4. University of California Santa Barbara, Santa Barbara, CA, USA

    • Aaron Bluestone
    • , Nicolas Volet
    • , Tin Komljenovic
    • , Lin Chang
    • , Luke Theogarajan
    •  & John E. Bowers
  5. California Institute of Technology, Pasadena, CA, USA

    • Seung Hoon Lee
    • , Dong Yoon Oh
    • , Myoung-Gyun Suh
    • , Ki Youl Yang
    •  & Kerry Vahala
  6. Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland

    • Martin H. P. Pfeiffer
    •  & Tobias J. Kippenberg
  7. Aurrion Inc., Goleta, CA, USA

    • Erik Norberg


  1. Search for Daryl T. Spencer in:

  2. Search for Tara Drake in:

  3. Search for Travis C. Briles in:

  4. Search for Jordan Stone in:

  5. Search for Laura C. Sinclair in:

  6. Search for Connor Fredrick in:

  7. Search for Qing Li in:

  8. Search for Daron Westly in:

  9. Search for B. Robert Ilic in:

  10. Search for Aaron Bluestone in:

  11. Search for Nicolas Volet in:

  12. Search for Tin Komljenovic in:

  13. Search for Lin Chang in:

  14. Search for Seung Hoon Lee in:

  15. Search for Dong Yoon Oh in:

  16. Search for Myoung-Gyun Suh in:

  17. Search for Ki Youl Yang in:

  18. Search for Martin H. P. Pfeiffer in:

  19. Search for Tobias J. Kippenberg in:

  20. Search for Erik Norberg in:

  21. Search for Luke Theogarajan in:

  22. Search for Kerry Vahala in:

  23. Search for Nathan R. Newbury in:

  24. Search for Kartik Srinivasan in:

  25. Search for John E. Bowers in:

  26. Search for Scott A. Diddams in:

  27. Search for Scott B. Papp in:


D.T.S., T.D., T.C.B. and J.S. contributed equally to performing the system measurements and analysing the experimental results. D.T.S., S.A.D. and S.B.P. prepared the manuscript. The integrated devices were fabricated and tested by Q.L., D.W., B.R.I. and K.S. (Si3N4); A.B., N.V., T.K., L.C. and E. N. (III–V/Si); and S.H.L., D.Y.O., M.S., K.Y.Y. and K.V. (SiO2). N.V., L.C.S., C.F., M.H.P.F. and A.B. provided measurement support. T.J.K, E.N., K.V., K.S., N.R.N., L.T., J.E.B., S.A.D. and S.B.P. supervised and led the scientific collaboration. This work is an official contribution of the NIST; not subject to copyright in the United States. The use of trade names is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Daryl T. Spencer or Scott B. Papp.

Extended data figures and tables

  1. Extended Data Fig. 1 Tuning details for III–V/Si laser.

    a, Typical tuning map of the III–V/Si tunable laser’s peak wavelength in nanometres versus current applied to each heater above the ring resonators. b, Normalized optical spectra showing >40 dB of side-mode suppression ratio across the tuning range. c, Typical unlocked RF beat notes between the tunable laser and the auxiliary comb for two different biases of the phase section. Careful control of the heater is required to reach all wavelengths in the tuning range, and reduction of the laser linewidth (blue to red) through longitudinal mode alignment and the optical feedback effect42 is required to achieve the best phase-locking performance to the microcombs. RBW, resolution bandwidth, VBW, video bandwidth.

  2. Extended Data Fig. 2 Demonstration of pumping the Si3N4 THz microcomb with the III–V/Si laser.

    a, Output optical spectrum of the THz microcomb showing dual-dispersive waves, as measured on two optical spectrum analysers. b, Comparison of electro-optic repetition rate detection43 when using the same III–V/Si laser (black) and external cavity diode laser (ECDL, red) from the main experiment to pump the THz microcomb.

About this article

Publication history







By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.