Non-reciprocal light propagation is essential to control optical crosstalk and back-scatter in photonic systems. However, realizing high-fidelity non-reciprocity in low-loss integrated photonic circuits remains challenging. Here, we experimentally demonstrate a form of non-local acousto-optic light scattering to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this system, a travelling-wave acoustic phonon driven by optical forces in a silicon waveguide spatiotemporally modulates light in a separate waveguide through linear interband Brillouin scattering. This process extends narrowband optomechanics-based schemes for non-reciprocity to travelling-wave physics, enabling large operation bandwidths of more than 125 GHz and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating optical waves. The modulator operation wavelength is tunable over a 35-nm range by varying the optical drive wavelength. Such travelling-wave acousto-optic interactions provide a promising path toward the realization of broadband, low-loss isolators and circulators within integrated photonics.

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This work was supported through a seedling grant under the direction of D. Green at DARPA MTO and by the Packard Fellowship for Science and Engineering; N.T.O. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant no. DGE1122492.

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  1. Department of Applied Physics, Yale University, New Haven, CT, USA

    • Eric A. Kittlaus
    • , Nils T. Otterstrom
    • , Prashanta Kharel
    • , Shai Gertler
    •  & Peter T. Rakich


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E.A.K. designed and fabricated the waveguide devices. E.A.K., P.K., S.G., N.T.O. and P.T.R. developed numerical and analytical models of the device physics. E.A.K., N.T.O. and S.G. conducted experiments with the assistance of P.K. and P.T.R. All authors contributed to the writing of this paper.

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The authors declare no competing interests.

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Correspondence to Eric A. Kittlaus or Peter T. Rakich.

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