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A Purcell-enabled monolayer semiconductor free-space optical modulator

Nature Photonics volume 17, pages 897–903 (2023)Cite this article

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Abstract

Dephasing and non-radiative decay processes limit the performance of a wide variety of quantum devices at room temperature. Here we illustrate a general pathway to notably reduce the detrimental impact of these undesired effects through photonic design of the device electrodes. Our design facilitates a large Purcell enhancement that speeds up competing, desired radiative decay while also enabling convenient electrical gating and charge injection functions. We demonstrate the concept with a free-space optical modulator based on an atomically thin semiconductor. By engineering the plasmonic response of a nanopatterned silver gate pad, we successfully enhance the radiative decay rate of excitons in a tungsten disulfide monolayer by one order of magnitude to create record-high modulation efficiencies for this class of materials at room temperature. We experimentally observe a 10% reflectance change as well as 3 dB signal modulation, corresponding to a 20-fold enhancement compared with modulation using a suspended monolayer in vacuum. We also illustrate how dynamic control of light fields can be achieved with designer surface patterns. This research highlights the benefits of applying radiative decay engineering as a powerful tool in creating high-performance devices that complements substantial efforts to improve the quality of materials.

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Fig. 1: Monolayer WS2 free-space optical modulator.
Fig. 2: Enhanced modulation with an silver metasurface gate pad.
Fig. 3: Intensity modulation of the reflected beam via electrical gating.
Fig. 4: Monolayer WS2 light-field modulators with a beam-steering function.

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Data availability

All key data that support the findings of this study are included in the article and its Supplementary Information. Further datasets and raw measurements are available from the corresponding author on reasonable request.

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Acknowledgements

We would like to acknowledge funding from an AFOSR MURI grant (grant no. FA9550-17-1-0002) and the US Department of Energy (grant no. DE-FG07-ER46426).

Author information

Author notes

  1. These authors contributed equally: Jung-Hwan Song, Fenghao Xu, Jorik van de Groep.

Authors and Affiliations

  1. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, USA

    Qitong Li, Jung-Hwan Song, Fenghao Xu, Jorik van de Groep, Jiho Hong, Yan Joe Lee & Mark L. Brongersma

  2. Van der Waals–Zeeman Institute for Experimental Physics, Institute of Physics, University of Amsterdam, Amsterdam, the Netherlands

    Jorik van de Groep

  3. Department of Electrical Engineering, Stanford University, Stanford, CA, USA

    Alwin Daus & Eric Pop

  4. Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA

    Amalya C. Johnson

  5. Department of Chemistry, Stanford University, Stanford, CA, USA

    Fang Liu

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  1. Qitong Li
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Contributions

Q.L. and M.L.B. conceived the research idea. Q.L. built the model, performed the design and fabrication of optical modulators with input from J.v.d.G. Q.L., J.-H.S. and F.X. performed the experimental characterization of the optical modulators. A.C.J. and F.L. prepared monolayer WS2 samples. J.H. performed wire-bonding for electrical characterization. A.D. and E.P. helped with atomic layer deposition. Y.J.L. helped with photoluminescence measurement. M.L.B. supervised the project. All of the authors contributed to writing the manuscript.

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Correspondence to Mark L. Brongersma.

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Nature Photonics thanks Alex Krasnok and Zongfu Yu for their contribution to the peer review of this work.

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Supplementary Notes 1–3 and Figs. 1–19.

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Li, Q., Song, JH., Xu, F. et al. A Purcell-enabled monolayer semiconductor free-space optical modulator. Nat. Photon. 17, 897–903 (2023). https://doi.org/10.1038/s41566-023-01250-9

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