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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.

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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.


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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




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.

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Peer review information Nature Physics thanks Tal Carmon and Gustavo Wiederhecker for their contribution to the peer review of this work.

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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.

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

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