Large Pockels effect in micro- and nanostructured barium titanate integrated on silicon

Abstract

The electro-optical Pockels effect is an essential nonlinear effect used in many applications. The ultrafast modulation of the refractive index is, for example, crucial to optical modulators in photonic circuits. Silicon has emerged as a platform for integrating such compact circuits, but a strong Pockels effect is not available on silicon platforms. Here, we demonstrate a large electro-optical response in silicon photonic devices using barium titanate. We verify the Pockels effect to be the physical origin of the response, with r42 = 923 pm V−1, by confirming key signatures of the Pockels effect in ferroelectrics: the electro-optic response exhibits a crystalline anisotropy, remains strong at high frequencies, and shows hysteresis on changing the electric field. We prove that the Pockels effect remains strong even in nanoscale devices, and show as a practical example data modulation up to 50 Gbit s−1. We foresee that our work will enable novel device concepts with an application area largely extending beyond communication technologies.

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Fig. 1: Fabrication process and structural characterization for a hybrid crystalline–amorphous BTO–SiO2 heterostructure.
Fig. 2: Layout of the photonic and plasmonic devices.
Fig. 3: EO response proving the presence of the Pockels effect.
Fig. 4: Data transmission in a photonic and plasmonic modulator.

Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

This project received funding from the European Commission under grant agreement nos FP7-ICT-2013-11-619456 (SITOGA), H2020-ICT-2015-25-688579 (PHRESCO), 688282 (PETMEM) and H2020-ICT-2017-1-780997 (plaCMOS), from the Swiss State Secretariat for Education, Research and Innovation under contract nos 15.0285 and 16.0001, and from the Swiss National Foundation project no. 200021_159565 (PADOMO). J.E.O. and A.A.D. acknowledge support from the Air Force Office of Scientific Research under grant FA9550–12–10494 and from the National Science Foundation under grant no. IRES-1358111. J.E.O. is grateful for generous support from the National Science Foundation Graduate Research Fellowship under grant no. DGE-1610403. P.S. acknowledges funding from project TEC2016-76849 (MINECO/FEDER, UE).

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Contributions

S.A., F.E. and J.F. fabricated and structurally characterized the epitaxial BTO and STO layers. S.A., J.F. and P.S. defined the photonics device concept (photonics), and P.M., J.L. and J.F. the plasmonics concept. The concepts were refined and implemented by S.A. and F.E. (photonics) and by A.M., F.E. and P.M. (plasmonics). S.A., D.C. and F.E. fabricated the photonic devices and F.E. the plasmonic devices. S.A., J.E.O. (as a visiting scientist at IBM) and L.C. characterized the EO performance of the photonic devices. P.C., A.R., A.M.G. and J.E.O. performed the data communication experiments on the photonic structures and analysed the data together (with P.S. and D.T.). A.M., F.E., A.J., B.B. and W.H. characterized the EO performance of plasmonic devices and analysed the data. F.E. performed all TEM investigations. T.W. and S.A. performed and analysed the KFM experiments. D.U., J.E.O. and S.A. performed the simulation of the photonic devices. A.M. performed the simulations of the plasmonic devices. S.A., F.E. and J.F. wrote the manuscript, with the support of all authors. S.A., P.M., P.S. and A.D. bear responsibility for the contributions to the manuscript emanating from their team.

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Correspondence to Stefan Abel or Ping Ma or Pablo Sanchis.

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Supplementary Notes 1–11, Supplementary Figures 1–25, Supplementary Tables 1–3, Supplementary References 1–23

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Abel, S., Eltes, F., Ortmann, J.E. et al. Large Pockels effect in micro- and nanostructured barium titanate integrated on silicon. Nature Mater 18, 42–47 (2019). https://doi.org/10.1038/s41563-018-0208-0

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