Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Strong optical coupling through superfluid Brillouin lasing


Brillouin scattering has applications ranging from signal processing1,2, sensing3 and microscopy4 to quantum information5 and fundamental science6,7. Most of these applications rely on the electrostrictive interaction between light and phonons3,7,8. Here we show that in liquids optically induced surface deformations can provide an alternative and far stronger interaction. This allows the demonstration of ultralow-threshold Brillouin lasing and strong phonon-mediated optical coupling. This form of strong coupling is a key capability for Brillouin-reconfigurable optical switches and circuits9,10, for photonic quantum interfaces11 and to generate synthetic electromagnetic fields12,13. While applicable to liquids quite generally, our demonstration uses superfluid helium. Configured as a Brillouin gyroscope14 this provides the prospect of measuring superfluid circulation with unprecedented precision, and exploring the rich physics of quantum fluid dynamics, from quantized vorticity to quantum turbulence15,16.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Brillouin scattering with compliant fluid interfaces.
Fig. 2: Schematic of the experimental set-up.
Fig. 3: Tuning from standing-wave optomechanics to travelling-wave Brillouin lasing.
Fig. 4: Strong phonon-mediated optical coupling.

Data availability

The data represented in Figs. 3b–d and 4 are available as Source Data. All other data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.

Code availability

All relevant codes or algorithms are available from the corresponding author on reasonable request.


  1. Kittlaus, E. A., Otterstrom, N. T. & Rakich, P. T. On-chip inter-modal Brillouin scattering. Nat. Commun. 8, 15819 (2017).

    ADS  Google Scholar 

  2. Li, J., Lee, H. & Vahala, K. J. Microwave synthesizer using an on-chip Brillouin oscillator. Nat. Commun. 4, 2097 (2013).

    ADS  Google Scholar 

  3. Eggleton, B. J., Poulton, C. G. & Pant, R. Inducing and harnessing stimulated Brillouin scattering in photonic integrated circuits. Adv. Opt. Photon. 5, 536–587 (2013).

    Google Scholar 

  4. Scarcelli, G. & Yun, S. H. Confocal Brillouin microscopy for three-dimensional mechanical imaging. Nat. Photon. 2, 39–43 (2008).

    ADS  Google Scholar 

  5. Renninger, W. H., Kharel, P., Behunin, R. O. & Rakich, P. T. Bulk crystalline optomechanics. Nat. Phys. 14, 601–607 (2018).

    Google Scholar 

  6. Kharel, P. et al. High-frequency cavity optomechanics using bulk acoustic phonons. Sci. Adv. 5, eaav0582 (2019).

    ADS  Google Scholar 

  7. Kashkanova, A. D. et al. Superfluid Brillouin optomechanics. Nat. Phys. 13, 74–79 (2017).

    Google Scholar 

  8. Giorgini, A. et al. Stimulated Brillouin cavity optomechanics in liquid droplets. Phys. Rev. Lett. 120, 073902 (2018).

    ADS  Google Scholar 

  9. Ruesink, F., Mathew, J. P., Miri, M.-A., Alù, A. & Verhagen, E. Optical circulation in a multimode optomechanical resonator. Nat. Commun. 9, 1798 (2018).

    ADS  Google Scholar 

  10. Shen, Z. et al. Reconfigurable optomechanical circulator and directional amplifier. Nat. Commun. 9, 1797 (2018).

    ADS  Google Scholar 

  11. Safavi-Naeini, A. H. & Painter, O. Proposal for an optomechanical traveling wave phonon–photon translator. New J. Phys. 13, 013017 (2011).

    ADS  Google Scholar 

  12. Fang, K. et al. Generalized non-reciprocity in an optomechanical circuit via synthetic magnetism and reservoir engineering. Nat. Phys. 13, 465–471 (2017).

    Google Scholar 

  13. Schmidt, M., Kessler, S., Peano, V., Painter, O. & Marquardt, F. Optomechanical creation of magnetic fields for photons on a lattice. Optica 2, 635–641 (2015).

    ADS  Google Scholar 

  14. Li, J., Suh, M. & Vahala, K. Microresonator Brillouin gyroscope. Optica 4, 346–348 (2017).

    ADS  Google Scholar 

  15. Sachkou, Y. P. et al. Coherent vortex dynamics in a strongly interacting superfluid on a silicon chip. Science 366, 1480–1485 (2019).

    ADS  Google Scholar 

  16. Gauthier, G. et al. Giant vortex clusters in a two-dimensional quantum fluid. Science 364, 1264–1267 (2019).

    ADS  MathSciNet  MATH  Google Scholar 

  17. Reinke, C., Rakich, P. T., Wang, Z., Camacho, R. & Davids, P. Giant enhancement of stimulated Brillouin scattering in the subwavelength limit. Phys. Rev. X 2, 011008 (2012).

    Google Scholar 

  18. Kittlaus, E. A., Shin, H. & Rakich, P. T. Large Brillouin amplification in silicon. Nat. Photon. 10, 463–467 (2016).

    ADS  Google Scholar 

  19. Florez, O. et al. Brillouin scattering self-cancellation. Nat. Commun. 7, 11759 (2016).

    ADS  Google Scholar 

  20. Van Laer, R., Kuyken, B., Van Thourhout, D. & Baets, R. Interaction between light and highly confined hypersound in a silicon photonic nanowire. Nat. Photon. 9, 199–203 (2015).

    ADS  Google Scholar 

  21. Shin, H. et al. Tailorable stimulated Brillouin scattering in nanoscale silicon waveguides. Nat. Commun. 4, 1944 (2013).

    ADS  Google Scholar 

  22. Enzian, G. et al. Observation of Brillouin optomechanical strong coupling with an 11 GHz mechanical mode. Optica 6, 7–14 (2019).

    ADS  Google Scholar 

  23. Gundavarapu, S. et al. Sub-hertz fundamental linewidth photonic integrated Brillouin laser. Nat. Photon. 13, 60–67 (2019).

    ADS  Google Scholar 

  24. Dong, C. H. et al. Brillouin-scattering-induced transparency and non-reciprocal light storage. Nat. Commun. 6, 6193 (2015).

    ADS  Google Scholar 

  25. Wolff, C., Steel, M. J., Eggleton, B. J. & Poulton, C. G. Stimulated Brillouin scattering in integrated photonic waveguides: forces, scattering mechanisms, and coupled-mode analysis. Phys. Rev. A 92, 013836 (2015).

    ADS  Google Scholar 

  26. Kaminski, S., Martin, L. L., Maayani, S. & Carmon, T. Ripplon laser through stimulated emission mediated by water waves. Nat. Photon. 10, 758–761 (2016).

    ADS  Google Scholar 

  27. Harris, G. I. et al. Laser cooling and control of excitations in superfluid helium. Nat. Phys. 12, 788–793 (2016).

    Google Scholar 

  28. Baker, C. G. et al. Theoretical framework for thin film superfluid optomechanics: towards the quantum regime. New J. Phys. 18, 123025 (2016).

    ADS  Google Scholar 

  29. Bahl, G., Tomes, M., Marquardt, F. & Carmon, T. Observation of spontaneous Brillouin cooling. Nat. Phys. 8, 203–207 (2012).

    Google Scholar 

  30. Bahl, G. et al. Brillouin cavity optomechanics with microfluidic devices. Nat. Commun. 4, 2994 (2013).

    Google Scholar 

  31. McAuslan, D. L. et al. Microphotonic forces from superfluid flow. Phys. Rev. X 6, 021012 (2016).

    Google Scholar 

  32. Atkins, K. R. Third and fourth sound in liquid helium II. Phys. Rev. 113, 962–965 (1959).

    ADS  Google Scholar 

  33. Ashkin, A., Dziedzic, J. M., Bjorkholm, J. E. & Chu, S. Observation of a single-beam gradient force optical trap for dielectric particles. Opt. Lett. 11, 288–290 (1986).

    ADS  Google Scholar 

  34. Wiederhecker, G. S., Dainese, P. & MayerAlegre, T. P. Brillouin optomechanics in nanophotonic structures. APL Photon. 4, 071101 (2019).

    ADS  Google Scholar 

  35. Rakich, P. & Marquardt, F. Quantum theory of continuum optomechanics. New J. Phys. 20, 045005 (2018).

    ADS  Google Scholar 

  36. Van Laer, R., Baets, R. & Van Thourhout, D. Unifying Brillouin scattering and cavity optomechanics. Phys. Rev. A 93, 053828 (2016).

    ADS  Google Scholar 

  37. Metzger, C. H. & Karrai, K. Cavity cooling of a microlever. Nature 432, 1002–1005 (2004).

    ADS  Google Scholar 

  38. Jourdan, G., Comin, F. & Chevrier, J. Mechanical mode dependence of bolometric backaction in an atomic force microscopy microlever. Phys. Rev. Lett. 101, 133904 (2008).

    ADS  Google Scholar 

  39. Verhagen, E., Deleglise, S., Weis, S., Schliesser, A. & Kippenberg, T. J. Quantum-coherent coupling of a mechanical oscillator to an optical cavity mode. Nature 482, 63–67 (2012).

    ADS  Google Scholar 

  40. Zhu, J. et al. On-chip single nanoparticle detection and sizing by mode splitting in an ultrahigh- Q microresonator. Nat. Photon. 4, 46–49 (2010).

    ADS  Google Scholar 

  41. Grudinin, I. S., Matsko, A. B. & Maleki, L. Brillouin lasing with a CaF2 whispering gallery mode resonator. Phys. Rev. Lett. 102, 043902 (2009).

    ADS  Google Scholar 

  42. Lee, H. et al. Chemically etched ultrahigh- Q wedge-resonator on a silicon chip. Nat. Photon. 6, 369–373 (2012).

    ADS  Google Scholar 

  43. Guo, C. et al. Ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation. Opt. Lett. 40, 4971–4974 (2015).

    ADS  Google Scholar 

  44. Feng, X. L., White, C. J., Hajimiri, A. & Roukes, M. L. A self-sustaining ultrahigh-frequency nanoelectromechanical oscillator. Nat. Nanotechnol. 3, 342–346 (2008).

    ADS  Google Scholar 

  45. Destgeer, G. & Sung, H. J. Recent advances in microfluidic actuation and micro-object manipulation via surface acoustic waves. Lab Chip 15, 2722–2738 (2015).

    Google Scholar 

  46. Palombo, F. & Fioretto, D. Brillouin light scattering: applications in biomedical sciences. Chem. Rev. 119, 7833–7847 (2019).

    Google Scholar 

Download references


This work was funded by the US Army Research Office through grant number W911NF17-1-0310 and the Australian Research Council Centre of Excellence for Engineered Quantum Systems (EQUS, project number CE170100009). W.P.B. and C.G.B respectively acknowledge Australian Research Council Fellowships FT140100650 and DE190100318. This work was performed in part at the Queensland node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano- and microfabrication facilities for Australia’s researchers.

Author information

Authors and Affiliations



X.H., G.I.H., C.G.B., A.S. and Y.L.S. collected the data. X.H., G.I.H., C.G.B., A.S., Y.L.S. and W.P.B. performed the data analysis and developed the theory. X.H., G.I.H., C.G.B., A.S., Y.L.S., Y.P.S. and S.F. contributed to device fabrication and building the experimental set-up. C.G.B. and W.P.B. conceived the idea. All authors contributed to the manuscript. W.P.B. led the project with assistance from C.G.B. and G.I.H.

Corresponding author

Correspondence to Christopher G. Baker.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Physics thanks Tal Carmon and Gustavo Wiederhecker 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.

Supplementary information

Supplementary Information

Supplementary information: 26 pages; 13 figures.

Source data

Source Data Fig. 3

Source data for the plots of Fig. 3 in the main text.

Source Data Fig. 4

Source data for the plots of Fig. 4 in the main text.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

He, X., Harris, G.I., Baker, C.G. et al. Strong optical coupling through superfluid Brillouin lasing. Nat. Phys. 16, 417–421 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing