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Exciton resonance tuning of an atomically thin lens

Abstract

The highly engineerable scattering properties of resonant optical antennas underpin the operation of metasurface-based flat optics. Thus far, the choice of antenna has been limited to shaped metallic and high-index semiconductor nanostructures that support geometrical plasmonic or Mie resonances. Whereas these resonant elements offer strong light–matter interaction and excellent control over the scattering phase and amplitude, their electrical tunability has proven to be quite limited. Here, we demonstrate how excitonic resonances in atomically thin semiconductors can be harnessed as a different, third type of resonance to create mutable, flat optics. These strong materials-based resonances are unmatched in their tunability with various external stimuli. To illustrate the concept, we first demonstrate how excitons can enhance the focusing efficiency of a millimetre-scale, patterned WS2 zone plate lens. We also show how electrical gating can completely turn on and off the exciton resonance and thereby modulate the focusing efficiency by 33%.

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Fig. 1: Atomically thin and tunable flat lenses.
Fig. 2: Material susceptibility and focusing efficiency.
Fig. 3: Exciton manipulation through ionic-liquid gating.
Fig. 4: Exciton modulation of the intensity in the focus.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We gratefully acknowledge useful discussions with M. Gebbie. This work was supported by the US Air Force (grant no. AnchorFA9550-17-1-0331). Some of the optical measurements were funded by the DOE ‘Photonics at Thermodynamic Limits’ Energy Frontier Research Center under grant DE-SC0019140. J.v.d.G. was also supported by a Rubicon Fellowship from the ‘Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)’. J.-H.S. was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1A6A3A03012480). U.C. acknowledges the partial support from the Fonds voor Wetenschappelijk Onderzoek—Vlaanderen (FWO). Part of this work was performed at the Nano@Stanford labs, supported by the National Science Foundation under award ECCS-1542152.

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J.v.d.G. and M.L.B. conceived the concepts behind this research. J.v.d.G. and J.-H.S. fabricated the samples and performed the optical measurements. U.C. performed the (conductive) AFM measurements. J.v.d.G., J.-H.S., Q.L., P.G.K. and M.L.B. performed the data analysis and calculations. All authors contributed to writing the manuscript.

Corresponding author

Correspondence to Mark L. Brongersma.

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Supplementary Figs. 1–11 and Notes 1 and 2.

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van de Groep, J., Song, JH., Celano, U. et al. Exciton resonance tuning of an atomically thin lens. Nat. Photonics 14, 426–430 (2020). https://doi.org/10.1038/s41566-020-0624-y

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