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A graphene-based broadband optical modulator

Nature volume 474, pages 6467 (02 June 2011) | Download Citation

Abstract

Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects1,2. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties3. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms4,5,6. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances7. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm2, which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

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Acknowledgements

This work was supported by the National Science Foundation Nano-scale Science and Engineering Center (NSF-NSEC) for Scalable and Integrated Nano Manufacturing (SINAM) (grant no. CMMI-0751621) and by the US Department of Energy, Basic Energy Sciences Energy Frontier Research Center (DoE-LMI-EFRC) under award DOE DE-AC02-05CH11231. M.L. thanks Y. Rao for discussions.

Author information

Author notes

    • Ming Liu
    •  & Xiaobo Yin

    These authors contributed equally to this work.

Affiliations

  1. NSF Nano-scale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California at Berkeley, Berkeley, California 94720, USA

    • Ming Liu
    • , Xiaobo Yin
    • , Erick Ulin-Avila
    • , Thomas Zentgraf
    •  & Xiang Zhang
  2. Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA

    • Baisong Geng
    • , Long Ju
    •  & Feng Wang
  3. Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA

    • Feng Wang
    •  & Xiang Zhang

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Contributions

M.L. and X.Z. contributed to the experimental ideas. M.L. fabricated device samples. M.L. and X.Y. carried out measurements, analysed the experimental data and prepared the manuscript. B.G., L.J. and F.W. prepared graphene film. All authors contributed to discussions and manuscript revision.

Competing interests

International patent applications may be affected by the paper.

Corresponding authors

Correspondence to Feng Wang or Xiang Zhang.

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DOI

https://doi.org/10.1038/nature10067

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