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Photonic microwave generation in the X- and K-band using integrated soliton microcombs

Nature Photonics volume 14, pages 486–491 (2020)Cite this article

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An Author Correction to this article was published on 18 May 2020

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Abstract

Microwave photonic technologies, which upshift the carrier into the optical domain, have facilitated the generation and processing of ultra-wideband electronic signals at vastly reduced fractional bandwidths. For microwave photonic applications such as radars, optical communications and low-noise microwave generation, optical frequency combs are useful building blocks. By virtue of soliton microcombs, frequency combs can now be built using CMOS-compatible photonic integrated circuits. Yet, currently developed integrated soliton microcombs all operate with repetition rates significantly beyond those that conventional electronics can detect, preventing their use in microwave photonics. Access to this regime is challenging due to the required ultra-low waveguide loss and large dimensions of the nanophotonic resonators. Here, we demonstrate soliton microcombs operating in two widely employed microwave bands, the X-band (~10 GHz, for radar) and the K-band (~20 GHz, for 5G). Driven by a low-noise fibre laser, these devices produce more than 300 frequency lines within the 3 dB bandwidth, and generate microwave signals featuring phase noise levels comparable to modern electronic microwave oscillators. Our results establish integrated microcombs as viable low-noise microwave generators. Furthermore, the low soliton repetition rates are critical for future dense wavelength-division multiplexing channel generation schemes and could significantly reduce the system complexity of soliton-based integrated frequency synthesizers and atomic clocks.

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Fig. 1: Principle of photonic microwave generation using integrated soliton microcombs and characteristics of the Si3N4 microresonators.
Fig. 2: Single solitons with microwave K- and X-band repetition rates.
Fig. 3: Phase noise characterization of the soliton repetition rate.
Fig. 4: Soliton injection-locking to an external microwave source.
Fig. 5: Comparison of compact photonics-based microwave generators.

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Data availability

The data that support the plots within this paper and other findings of this study are available on Zenodo (https://doi.org/10.5281/zenodo.3666737). All other data used in this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank N. J. Engelsen, G. Huang, W. Weng, M. A. Anderson and S. A. Bhave for discussions. This work was supported by contract no. FA9550-19-C-7001 (KECOMO) from the Defense Advanced Research Projects Agency (DARPA), Microsystems Technology Office (MTO), by the Air Force Office of Scientific Research, Air Force Materiel Command, USAF under award no. FA9550-15-1-0250, and by the Swiss National Science Foundation under grant no. 176563 (BRIDGE) and no. 165933. E.L. and M.K. acknowledge support from the European Space Technology Centre under ESA contract nos. 4000116145/16/NL/MH/GM and 4000118777/16/NL/GM, respectively. J.H. acknowledges support provided by H.-Y. Tam and the General Research Fund of the Hong Kong Government under project PolyU 152207/15E. H.G. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie IF grant no. 709249. The Si3N4 microresonator samples were fabricated in the EPFL Center of MicroNanoTechnology (CMi).

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Author notes

  1. Hairun Guo

    Present address: Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication, Shanghai Institute for Advanced Communication and Data Science, Shanghai University, Shanghai, China

  2. These authors contributed equally: Junqiu Liu, Erwan Lucas, Arslan S. Raja, Jijun He.

Authors and Affiliations

  1. Institute of Physics, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland

    Junqiu Liu, Erwan Lucas, Arslan S. Raja, Jijun He, Johann Riemensberger, Rui Ning Wang, Maxim Karpov, Hairun Guo, Romain Bouchand & Tobias J. Kippenberg

  2. Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China

    Jijun He

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Contributions

J.L. designed and fabricated the Si3N4 samples, with assistance from R.N.W. and H.G. Samples were characterized and analysed by J.L. and J.H. J.H., J.L., A.S.R. and M.K. performed the soliton generation experiment. E.L., A.S.R., J.R., J.L. and R.B. performed the phase noise measurements and the soliton injection-locking experiment. J.L., R.B., E.L. and T.J.K. wrote the manuscript, with input from the other authors. T.J.K. supervised the project.

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Correspondence to Tobias J. Kippenberg.

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Liu, J., Lucas, E., Raja, A.S. et al. Photonic microwave generation in the X- and K-band using integrated soliton microcombs. Nat. Photonics 14, 486–491 (2020). https://doi.org/10.1038/s41566-020-0617-x

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