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Electrically tunable space–time metasurfaces at optical frequencies

Nature Nanotechnology (2024)Cite this article

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Abstract

Active metasurfaces enable dynamic manipulation of the scattered electromagnetic wavefront by spatially varying the phase and amplitude across arrays of subwavelength scatterers, imparting momentum to outgoing light. Similarly, periodic temporal modulation of active metasurfaces allows for manipulation of the output frequency of light. Here we combine spatial and temporal modulation in electrically modulated reflective metasurfaces operating at 1,530 nm to generate and diffract a spectrum of sidebands at megahertz frequencies. Temporal modulation with tailored waveforms enables the design of a spectrum of sidebands. By impressing a spatial phase gradient on the metasurface, we can diffract selected combinations of sideband frequencies. Combining active temporal and spatial variation can enable unique optical functions, such as frequency mixing, harmonic beam steering or shaping, and breaking of Lorentz reciprocity.

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Fig. 1: Electrically controlled space–time metasurfaces.
Fig. 2: ITO-based plasmonic metasurface.
Fig. 3: Time modulation and waveform optimization.
Fig. 4: Diffraction of a single harmonic.
Fig. 5: Space–time modulation for arbitrary control over the spectral and spatial properties of light.

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Data availability

The authors declare that data supporting the findings of this study are available within the article and its Supplementary Information files. All the relevant data are available from the corresponding author upon request.

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Acknowledgements

This work was supported by the Air Force Office of Scientific Research Meta-Imaging MURI grant no. FA9550-21-1-0312 (J.S., P.T., M.G., R.S., I.H. and H.A.A.) and DARPA EXTREME (H.A.A.). J.S. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Postgraduate Scholarship – Doctoral program. P.T. acknowledges support from Meta Platforms, Inc., through the PhD fellowship #C-834952. We are grateful to Caltech colleagues O. Painter and A. Emami for support with waveform generation instrumentation. We further thank C. U. Hail, M. D. Kelzenberg and P. R. Jahelka for technical support and discussions.

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  1. These authors contributed equally: Jared Sisler, Prachi Thureja.

Authors and Affiliations

  1. Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology, Pasadena, CA, USA

    Jared Sisler, Prachi Thureja, Meir Y. Grajower, Ruzan Sokhoyan, Ivy Huang & Harry A. Atwater

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Contributions

J.S., P.T., M.Y.G., R.S. and H.A.A. conceived the ideas for this research project. J.S. and P.T. fabricated and characterized the active metasurfaces. J.S. and M.Y.G. built the experimental setup for time-modulation. J.S. and P.T. performed quasi-static and time-modulated measurements. J.S. built the setup for and performed the space–time measurements. J.S. created the real-time waveform optimization algorithm, with inputs from P.T. J.S. and M.Y.G. performed the space–time calculations. I.H. and P.T. designed the electrical PCB. All authors contributed to the writing of the manuscript.

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Correspondence to Harry A. Atwater.

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Nature Nanotechnology thanks Patrice Genevet, Guangwei Hu and Xingjie Ni for their contribution to the peer review of this work.

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Supplementary Sections 1–9 including detailed discussion and Supplementary Figs. 1–8.

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Sisler, J., Thureja, P., Grajower, M.Y. et al. Electrically tunable space–time metasurfaces at optical frequencies. Nat. Nanotechnol. (2024). https://doi.org/10.1038/s41565-024-01728-9

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