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Large Brillouin amplification in silicon


Both Kerr and Raman nonlinearities are radically enhanced by tight optical-mode confinement in nanoscale silicon waveguides1,2,3,4. Counterintuitively, Brillouin nonlinearities—originating from coupling between photons and acoustic phonons—are exceedingly weak in these same nonlinear waveguides5. Strong Brillouin interactions have only recently been realized in a new class of optomechanical structures that control the interaction between guided photons and phonons5,6,7. Despite these major advances, appreciable Brillouin-based optical amplification has yet to be observed in silicon. Using a membrane-suspended waveguide, we report large Brillouin amplification in silicon for the first time, reaching levels greater than 5 dB for modest pump powers, and demonstrate a record low (5 mW) threshold for net amplification. This work represents an important step towards the realization of high-performance Brillouin lasers and amplifiers in silicon.

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Figure 1: Hybrid photonic–phononic silicon waveguide.
Figure 2: Experimental results showing the Brillouin gain and net on-chip amplification.
Figure 3: Set-up and results of an energy-transfer (two-tone) experiment.


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Primary support for this work was provided by the MesoDynamic Architectures programme at DARPA under the direction of D. Green. This work was supported in part by the Packard Fellowship for Science and Engineering. H.S. acknowledges support from new faculty startup funding at POSTECH. We thank P. Kharel for technical discussions involving phononic systems and nonlinear interactions, and M. Rooks and M. Power for assistance with process development. We are grateful to R. Behunin, W. Renninger and W.P. Rakich for careful reading and critique of this manuscript.

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E.A.K. and H.S. fabricated the waveguide devices. P.T.R., H.S. and E.A.K. developed multiphysics simulations for and designed the devices. E.A.K. and H.S. conducted experiments with the assistance of P.T.R. P.T.R., H.S. and E.A.K. developed analytical models to interpret measured data. All authors contributed to the writing of this paper.

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Correspondence to Peter T. Rakich.

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The authors declare no competing financial interests.

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

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