Integrated turnkey soliton microcombs

Abstract

Optical frequency combs have a wide range of applications in science and technology1. An important development for miniature and integrated comb systems is the formation of dissipative Kerr solitons in coherently pumped high-quality-factor optical microresonators2,3,4,5,6,7,8,9. Such soliton microcombs10 have been applied to spectroscopy11,12,13, the search for exoplanets14,15, optical frequency synthesis16, time keeping17 and other areas10. In addition, the recent integration of microresonators with lasers has revealed the viability of fully chip-based soliton microcombs18,19. However, the operation of microcombs requires complex startup and feedback protocols that necessitate difficult-to-integrate optical and electrical components, and microcombs operating at rates that are compatible with electronic circuits—as is required in nearly all comb systems—have not yet been integrated with pump lasers because of their high power requirements. Here we experimentally demonstrate and theoretically describe a turnkey operation regime for soliton microcombs co-integrated with a pump laser. We show the appearance of an operating point at which solitons are immediately generated by turning the pump laser on, thereby eliminating the need for photonic and electronic control circuitry. These features are combined with high-quality-factor Si3N4 resonators to provide microcombs with repetition frequencies as low as 15 gigahertz that are fully integrated into an industry standard (butterfly) package, thereby offering compelling advantages for high-volume production.

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Fig. 1: Integrated soliton microcomb chip.
Fig. 2: The turnkey operating point.
Fig. 3: Optical and electrical spectra of solitons.
Fig. 4: Turnkey soliton generation.

Data availability

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

Code availability

The code used in this study is available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank G. Keeler, S. Papp, T. Briles, J. Norman and M. Tran for discussions, Y. Tong and S. Liu for assistance in characterizations, and Freedom Photonics for providing the lasers. The Si3N4 microresonators were fabricated at the EPFL Center of MicroNanoTechnology (CMi). This work is supported by the Defense Advanced Research Projects Agency (DARPA) under DODOS (HR0011-15-C-055) programmes of the Microsystems Technology Office (MTO).

Author information

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Authors

Contributions

B.S., L.C., Q.-F.Y., J.L., T.J.K., J.E.B. and K.V. conceived the experiment. D.K., L.C., B.S. and Q.-F.Y. packaged the chip. J.L., R.N.W., J.H. and T.L. designed, fabricated and tested the Si3N4 chip devices. H.W. constructed the theoretical model. Measurements were performed by B.S., L.C. and Q.-F.Y. with assistance from H.W., C.X., W.X., J.G., L.W. and Q.-X.J. All authors analysed the data and contributed to writing the manuscript. J.E.B., K.V. and T.J.K. supervised the project and the collaboration.

Corresponding authors

Correspondence to Lin Chang or Tobias J. Kippenberg or Kerry Vahala.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Luigi Lugiato and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Extended data figures and tables

Extended Data Fig. 1 Images and characteristics of microcomb resonators and pump lasers.

a, Photograph of Si3N4 microresonator chip devices. b, Scanning electron microscope image of the smooth facet of a Si3N4 chip. The Si3N4 inverse taper for butt-coupling is shown in blue. c, Microscopic image of a chip with ten DFB lasers. d, Light–current curve (blue; left vertical axis) and the wavelength response (red; right vertical axis) of the DFB laser.

Supplementary information

41586_2020_2358_MOESM2_ESM.mov

Conventional solitons are generated by sweeping the laser frequency. The normalized laser frequency αL is swept from −2 to 6 within a normalized time interval of 400. Parameters are K = 0 (no feedback) and |F|2 = 4. Left panel: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panel: Snapshots of the soliton field (upper) and optical spectrum (lower).

41586_2020_2358_MOESM3_ESM.mov

Multiple solitons are generated via feedback locking. Parameters are K = 15, ϕ = 0.15π, |F|2 = 3 and αL = 5. Left panels: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panels: Snapshots of the soliton field (upper) and optical spectrum (lower).

41586_2020_2358_MOESM4_ESM.mov

A single soliton is generated via injection locking. Parameters are K = 15, ϕ = 0.3π, |F|2 = 3 and αL = 5. Left panels: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panels: Snapshots of the soliton field (upper) and optical spectrum (lower).

Supplementary Information

This file contains theory and additional measurements, including Supplementary Figures S1–S4 and Supplementary References.

Supplementary Video 1

Conventional solitons are generated by sweeping the laser frequency. The normalized laser frequency αL is swept from −2 to 6 within a normalized time interval of 400. Parameters are K = 0 (no feedback) and |F|2 = 4. Left panel: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panel: Snapshots of the soliton field (upper) and optical spectrum (lower).

Supplementary Video 2

Multiple solitons are generated via feedback locking. Parameters are K = 15, ϕ = 0.15π, |F|2 = 3 and αL = 5. Left panels: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panels: Snapshots of the soliton field (upper) and optical spectrum (lower).

Supplementary Video 3

A single soliton is generated via injection locking. Parameters are K = 15, ϕ = 0.3π, |F|2 = 3 and αL = 5. Left panels: Soliton field power distribution as a function of evolution time and coordinates (upper) and dynamics of pump mode power and comb power (lower). Right panels: Snapshots of the soliton field (upper) and optical spectrum (lower).

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Shen, B., Chang, L., Liu, J. et al. Integrated turnkey soliton microcombs. Nature 582, 365–369 (2020). https://doi.org/10.1038/s41586-020-2358-x

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