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Non-Hermitian hybrid silicon photonic switching

Nature Photonics volume 19, pages 264–270 (2025)Cite this article

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Abstract

Leveraging the entire space of complex dielectric permittivity, non-Hermitian photonics has fundamentally altered wave propagation with complex optical potentials and has ushered in a host of new photonic applications. Through parity–time symmetry and its breaking—a delicate interplay between gain and loss—even the interaction between just two entities becomes counter-intuitive and intriguing. Here we realize, through hybrid III–V/Si integration, a scalable non-Hermitian switching network on a two-layer integrated photonic chip. Our platform is a hybrid, with a bottom silicon layer and a top InGaAsP layer that provides optical gain. By tuning the gain level in the top layer, vertically coupled waveguides operate below or above the exceptional point, where light is switched across two layers, among different input–output ports. For a single switching unit, the switching dynamics are ultrafast, on the order of 100 ps. In a large switching network, non-blocking and other diverse connectivities are established in single-wavelength and wavelength-selective switching, with high extinction ratios. Our approach adds scalable non-Hermitian switching to photonic design toolkits to simultaneously boost the switching time and bandwidth density to cutting-edge levels, therefore paving the way for compact and ultrafast monolithic integrated silicon photonics in next-generation optical information networks.

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Fig. 1: III–V/Si hybrid photonic switch.
Fig. 2: Characterization of a single switch unit.
Fig. 3: Characterization of an 8 × 8 switch.
Fig. 4: Demonstration of WSS.

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Data availability

Source data are provided with this paper. All other data that support other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We acknowledge support from the Army Research Office (ARO) (W911NF-21-1-0148 and W911NF-22-1-0140), the Office of Naval Research (ONR) (N00014-23-1-2882) and the National Science Foundation (NSF) (ECCS-2023780, DMR-2117775, DMR-2326698 and DMR-2326699). This work was carried out in part at the Singh Center for Nanotechnology, which is supported by the NSF National Nanotechnology Coordinated Infrastructure Program under grant no. NNCI-1542153.

Author information

Authors and Affiliations

  1. Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, USA

    Xilin Feng, Haoqi Zhao & Liang Feng

  2. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA

    Tianwei Wu, Zihe Gao, Shuang Wu, Yichi Zhang & Liang Feng

  3. Department of Physics and Astronomy, College of Staten Island, CUNY, Staten Island, NY, USA

    Li Ge

  4. The Graduate Center, CUNY, New York, NY, USA

    Li Ge

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Contributions

L.F. and X.F. designed the experiment. X.F., T.W., Z.G., L.G. and L.F. designed the photonic switch. X.F., T.W. and L.G. constructed the theoretical model. X.F. performed numerical simulations and fabricated the sample. X.F., T.W., Z.G., H.Z. and Y.Z. performed the measurements. X.F. and S.W. performed the data processing. X.F., S.W., L.G. and L.F. prepared the manuscript. All the authors contributed to the discussions.

Corresponding author

Correspondence to Liang Feng.

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Nature Photonics thanks the anonymous reviewers for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1

Fabrication flow of the III-V/Si hybrid photonic switch.

Extended Data Fig. 2 Schematic of experimental setup.

Blue line: pump beam. Red line: signal beam. ND: neutral density. HWP: half-wave plate. PBS: polarizing beamsplitter. BPF: bandpass filter. FM: flip mirror. BS: beamsplitter. SPAD: single photon avalanche diode.

Supplementary information

Supplementary Information

Supplementary Figs. 1–14 and discussion.

Source data

Source Data Fig. 2

Source data for Fig. 2b–d.

Source Data Fig. 3

Source data for Fig. 3e–g.

Source Data Fig. 4

Source data for Fig. 4b–e.

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Feng, X., Wu, T., Gao, Z. et al. Non-Hermitian hybrid silicon photonic switching. Nat. Photon. 19, 264–270 (2025). https://doi.org/10.1038/s41566-024-01579-9

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