Broadband electro-optic frequency comb generation in a lithium niobate microring resonator

Abstract

Optical frequency combs consist of equally spaced discrete optical frequency components and are essential tools for optical communication, precision metrology, timing and spectroscopy1,2,3,4,5,6,7,8,9. At present, combs with wide spectra are usually generated by mode-locked lasers10 or dispersion-engineered resonators with third-order Kerr nonlinearity11. An alternative method of comb production uses electro-optic (EO) phase modulation in a resonator with strong second-order nonlinearity, resulting in combs with excellent stability and controllability12,13,14. Previous EO combs, however, have been limited to narrow widths by a weak EO interaction strength and a lack of dispersion engineering in free-space systems. Here we overcome these limitations by realizing an integrated EO comb generator in a thin-film lithium niobate photonic platform that features a large EO response, ultralow optical loss and highly co-localized microwave and optical fields15, while enabling dispersion engineering. Our measured EO comb spans more frequencies than the entire telecommunications L-band (over 900 comb lines spaced about 10 gigahertz apart), and we show that future dispersion engineering can enable octave-spanning combs. Furthermore, we demonstrate the high tolerance of our comb generator to modulation frequency detuning, with frequency spacing finely controllable over seven orders of magnitude (10 hertz to 100 megahertz), and we use this feature to generate dual-frequency combs in a single resonator. Our results show that integrated EO comb generators are capable of generating wide and stable comb spectra. Their excellent reconfigurability is a powerful complement to integrated Kerr combs, enabling applications ranging from spectroscopy16 to optical communications8.

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Fig. 1: Resonator-enhanced EO comb generator.
Fig. 2: Integrated EO comb generator.
Fig. 3: Controllability of the EO comb spectrum.
Fig. 4: Dual-tone EO comb generation

Data availability

The datasets generated and analysed during the current study are available from the corresponding authors on reasonable request.

References

  1. 1.

    Ye, J., Schnatz, H. & Hollberg, L. W. Optical frequency combs: from frequency metrology to optical phase control. IEEE J. Sel. Top. Quantum Electron. 9, 1041–1058 (2003).

    CAS  ADS  Article  Google Scholar 

  2. 2.

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

    CAS  ADS  Article  Google Scholar 

  3. 3.

    Coddington, I., Newbury, N. & Swann, W. Dual-comb spectroscopy. Optica 3, 414–426 (2016).

    ADS  Article  Google Scholar 

  4. 4.

    Bernhardt, B. et al. Cavity-enhanced dual-comb spectroscopy. Nat. Photon. 4, 55–57 (2010).

    CAS  ADS  Article  Google Scholar 

  5. 5.

    Dutt, A. et al. On-chip dual-comb source for spectroscopy. Sci. Adv. 4, e1701858 (2018).

    ADS  Article  Google Scholar 

  6. 6.

    Suh, M.-G., Yang, Q.-F., Yang, K. Y., Yi, X. & Vahala, K. J. Microresonator soliton dual-comb spectroscopy. Science 354, 600–603 (2016).

    CAS  ADS  Article  Google Scholar 

  7. 7.

    Trocha, P. et al. Ultrafast optical ranging using microresonator soliton frequency combs. Science 359, 887–891 (2018).

    CAS  ADS  Article  Google Scholar 

  8. 8.

    Pfeifle, J. et al. Coherent terabit communications with microresonator Kerr frequency combs. Nat. Photon. 8, 375–380 (2014).

    CAS  ADS  Article  Google Scholar 

  9. 9.

    Suh, M.-G. & Vahala, K. J. Soliton microcomb range measurement. Science 359, 884–887 (2018).

    CAS  ADS  Article  Google Scholar 

  10. 10.

    Cundiff, S. T., Ye, J. & Hall, J. L. Optical frequency synthesis based on mode-locked lasers. Rev. Sci. Instrum. 72, 3749–3771 (2001).

    CAS  ADS  Article  Google Scholar 

  11. 11.

    Kippenberg, T. J., Gaeta, A. L., Lipson, M. & Gorodetsky, M. L. Dissipative Kerr solitons in optical microresonators. Science 361, eaan8083 (2018).

    Article  Google Scholar 

  12. 12.

    Kourogi, M., Nakagawa, K. & Ohtsu, M. Wide-span optical frequency comb generator for accurate optical frequency difference measurement. IEEE J. Quantum Electron. 29, 2693–2701 (1993).

    CAS  ADS  Article  Google Scholar 

  13. 13.

    Beha, K. et al. Electronic synthesis of light. Optica 4, 406–411 (2017).

    CAS  ADS  Article  Google Scholar 

  14. 14.

    Xiao, S., Hollberg, L., Newbury, N. R. & Diddams, S. A. Toward a low-jitter 10 GHz pulsed source with an optical frequency comb generator. Opt. Express 16, 8498–8508 (2008).

    ADS  Article  Google Scholar 

  15. 15.

    Wang, C. et al. Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages. Nature 562, 101–104 (2018).

    CAS  ADS  Article  Google Scholar 

  16. 16.

    Millot, G. et al. Frequency-agile dual-comb spectroscopy. Nat. Photon. 10, 27–30 (2016).

    CAS  ADS  Article  Google Scholar 

  17. 17.

    Del’Haye, P. et al. Octave spanning tunable frequency comb from a microresonator. Phys. Rev. Lett. 107, 063901 (2011).

    ADS  Article  Google Scholar 

  18. 18.

    Okawachi, Y. et al. Octave-spanning frequency comb generation in a silicon nitride chip. Opt. Lett. 36, 3398–3400 (2011).

    CAS  ADS  Article  Google Scholar 

  19. 19.

    Griffith, A. G. et al. Silicon-chip mid-infrared frequency comb generation. Nat. Commun. 6, 6299 (2015).

    CAS  ADS  Article  Google Scholar 

  20. 20.

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

    ADS  Article  Google Scholar 

  21. 21.

    Liang, W. et al. Generation of near-infrared frequency combs from a MgF2 whispering gallery mode resonator. Opt. Lett. 36, 2290–2292 (2011).

    CAS  ADS  Article  Google Scholar 

  22. 22.

    Gräupner, P., Pommier, J. C., Cachard, A. & Coutaz, J. L. Electro-optical effect in aluminum nitride waveguides. J. Appl. Phys. 71, 4136–4139 (1992).

    ADS  Article  Google Scholar 

  23. 23.

    Herr, T. et al. Universal formation dynamics and noise of Kerr-frequency combs in microresonators. Nat. Photon. 6, 480–487 (2012).

    CAS  ADS  Article  Google Scholar 

  24. 24.

    Yi, X. et al. Single-mode dispersive waves and soliton microcomb dynamics. Nat. Commun. 8, 14869 (2017).

    CAS  ADS  Article  Google Scholar 

  25. 25.

    Metcalf, A. J., Torres-Company, V., Leaird, D. E. & Weiner, A. M. High-power broadly tunable electrooptic frequency comb generator. IEEE J. Sel. Top. Quantum Electron. 19, 231–236 (2013).

    ADS  Article  Google Scholar 

  26. 26.

    Sakamoto, T., Kawanishi, T. & Izutsu, M. Asymptotic formalism for ultraflat optical frequency comb generation using a Mach-Zehnder modulator. Opt. Lett. 32, 1515–1517 (2007).

    ADS  Article  Google Scholar 

  27. 27.

    Ozharar, S., Quinlan, F., Ozdur, I., Gee, S. & Delfyett, P. J. Ultraflat optical comb generation by phase-only modulation of continuous-wave light. IEEE Photonics Technol. Lett. 20, 36–38 (2008).

    ADS  Article  Google Scholar 

  28. 28.

    Ho, K. P. & Kahn, J. M. Optical frequency comb generator using phase modulation in amplified circulating loop. IEEE Photonics Technol. Lett. 5, 721–725 (1993).

    ADS  Article  Google Scholar 

  29. 29.

    Kourogi, M., Widiyatomoko, B., Takeuchi, Y. & Ohtsu, M. Limit of optical-frequency comb generation due to material dispersion. IEEE J. Quantum Electron. 31, 2120–2126 (1995).

    CAS  ADS  Article  Google Scholar 

  30. 30.

    Dupuis, N. et al. InP-based comb generator for optical OFDM. J. Lightwave Technol. 30, 466–472 (2012).

    CAS  ADS  Article  Google Scholar 

  31. 31.

    Demirtzioglou, I. et al. Frequency comb generation in a silicon ring resonator modulator. Opt. Express 26, 790–796 (2018).

    CAS  ADS  Article  Google Scholar 

  32. 32.

    Kim, J., Richardson, D. J. & Slavík, R. Cavity-induced phase noise suppression in a Fabry–Perot modulator-based optical frequency comb. Opt. Lett. 42, 1536–1539 (2017).

    CAS  ADS  Article  Google Scholar 

  33. 33.

    Kourogi, M., Enami, T. & Ohtsu, M. A coupled-cavity monolithic optical frequency comb generator. IEEE Photonics Technol. Lett. 8, 1698–1700 (1996).

    ADS  Article  Google Scholar 

  34. 34.

    Zhang, M., Wang, C., Cheng, R., Shams-Ansari, A. & Lončar, M. Monolithic ultra-high-Q lithium niobate microring resonator. Optica 4, 1536–1537 (2017).

    CAS  ADS  Article  Google Scholar 

  35. 35.

    Wang, C., Zhang, M., Stern, B., Lipson, M. & Lončar, M. Nanophotonic lithium niobate electro-optic modulators. Opt. Express 26, 1547–1555 (2018).

    ADS  Article  Google Scholar 

  36. 36.

    Kobayashi, T., Sueta, T., Cho, Y. & Matsuo, Y. High-repetition-rate optical pulse generator using a Fabry–Perot electro-optic modulator. Appl. Phys. Lett. 21, 341–343 (1972).

    CAS  ADS  Article  Google Scholar 

  37. 37.

    Saitoh, T. et al. Modulation characteristic of waveguide-type optical frequency comb generator. J. Lightwave Technol. 16, 824–832 (1998).

    ADS  Article  Google Scholar 

  38. 38.

    Kim, J., Richardson, D. J. & Slavík, R. In 2016 IEEE Photonics Conference (IPC) 503–504, https://doi.org/10.1109/IPCon.2016.7831201 (2016).

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Acknowledgements

This work is supported by the National Science Foundation (award numbers ECCS-1609549, ECCS-1740291 E2CDA, ECCS-1740296 E2CDA and DMR-1231319); the Harvard University Office of Technology Development (Physical Sciences and Engineering Accelerator Award); and Facebook, Inc. Device fabrication is performed at the Harvard University Center for Nanoscale Systems, a member of the National Nanotechnology Coordinated Infrastructure Network, which is supported by the National Science Foundation (award number ECCS-1541959).

Reviewer information

Nature thanks Yanne K. Chembo, Paulina Kuo and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Authors

Contributions

M.Z., B.B., C.W., J.M.K. and M.L. conceived the experiment. M.Z., C.W. and A.S.-A. designed and fabricated the devices. B.B. performed theoretical modelling and numerical simulations of the integrated EO comb. M.Z. and R.Z. designed waveguide dispersion. M.Z., C.W., A.S.-A. and C.R. carried out the device characterization. M.Z. and B.B. performed the data analysis. M.Z. and B.B. wrote the manuscript with contributions from all authors. J.M.K. and M.L. supervised the project.

Corresponding authors

Correspondence to Joseph M. Kahn or Marko Lončar.

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Competing interests

The authors declare competing interests: M.Z., C.W., C.R. and M.L. are involved in developing lithium niobate technologies at HyperLight Corporation.

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Extended data figures and tables

Extended Data Fig. 1 Dispersion engineering and tailored EO comb phase-matching condition.

a, Simulated dispersion for an air-clad lithium niobate ridge waveguide with top width w = 1,800 nm, film thickness t = 600 nm and etch depth h = 550 nm. b, The phase-matching condition for generating EO comb sidebands. The grey area shows the region of phase matching, with round-trip modulation strength β. With a 50-GHz microwave drive and β = 1.2π, an EO comb spanning 1.3 octaves can be generated. c, Simulated group velocity dispersion (GVD) for an air-clad lithium niobate waveguide with a different geometry optimized for an octave-spanning comb with small microwave driving amplitude. d, An octave-spanning EO comb is shown with β = 0.3π. e, Another example of an air-clad lithium niobate waveguide with dispersion engineered for broad comb generation. f, Such EO comb generation features a flat response over 600 nm. A broad comb spanning less than an octave can be generated in devices with small microwave modulation amplitudes and high-Q optical resonators.

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Zhang, M., Buscaino, B., Wang, C. et al. Broadband electro-optic frequency comb generation in a lithium niobate microring resonator. Nature 568, 373–377 (2019). https://doi.org/10.1038/s41586-019-1008-7

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