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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The data that support the findings of this study are available from the corresponding authors upon reasonable request.
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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).
The authors declare no competing interests.
Peer review information Nature thanks Luigi Lugiato and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data figures and tables
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.
This file contains theory and additional measurements, including Supplementary Figures S1–S4 and Supplementary References.
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).
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).
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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