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Coherent steering of nonlinear chiral valley photons with a synthetic Au–WS2 metasurface

Abstract

Two-dimensional transition metal dichalcogenides (TMDCs) present extraordinary nonlinearities and direct bandgaps at the K and K′ valleys. These valleys can be optically manipulated through, for example, plasmon–valley-exciton coupling with spin-dependent photoluminescence. However, the weak coherence between the pumping and emission makes exploring nonlinear valleytronic devices based on TMDCs challenging. Here, we show that a synthetic metasurface, which entangles the phase and spin of light, can simultaneously enhance and manipulate nonlinear valley-locked chiral emission in monolayer tungsten disulfide (WS2) at room temperature. The second-harmonic valley photons, accessed and coherently pumped by light, with a spin-related geometric phase imparted by a gold (Au) metasurface, are separated and routed to predetermined directions in free space. In addition, the nonlinear photons with the same spin as the incident light are steered owing to the critical spin–valley-locked nonlinear selection rule of WS2 in our designed metasurface. Our synthetic TMDC–metasurface interface may facilitate advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices.

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Fig. 1: Concept, main result and principle of the synthetic Au–WS2 metasurface.
Fig. 2: The optical set-up and experimental results under linearly polarized pumping.
Fig. 3: Schematic and experimental comparison for the synthetic Au–WS2 metasurface under RCP pumping.
Fig. 4: SHG enhancement in the synthetic Au–WS2 metasurface.

Data availability

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

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Acknowledgements

The work done at Huazhong University of Science and Technology was supported by the National Natural Science Foundation of China (grant numbers 91850113, 11774115 and 11674117) and the 973 Programs under grant number 2014CB921301. We thank the Center of Nano-Science and Technology of Wuhan University for their support in sample fabrication. J.W. acknowledges financial support from the A*Star – Science and Engineering Research Council Pharos Program (grant number 15270 00015). S.Z. acknowledges support from ERC Consolidator Award (TOPOLOGICAL). F.G.-V. acknowledges financial support from the Spanish MINECO under contract no. MAT2014-53432-C5-5-R and the “María de Maeztu” programme for Units of Excellence in R&D (MDM-2014-0377). C.-W.Q. acknowledges financial support from A*STAR Pharos Program (grant number 15270 00014, with project number R-263-000-B91-305) and the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Program (CRP award number NRFCRP 15-2015-03).

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K.W., P.L., C.-W.Q. and G.H. conceived the idea. K.W., P.L. and C.-W.Q. supervised the project. G.H., K.W. and C.-W.Q. designed the experiments. X.H., K.W., W.Z., W.L. and B.W. performed the experiments. G.H., J.W., K.W., H.-X.X., S.Z., F.G.-V., P.L. and C.-W.Q. analysed the data. G.H., F.G.-V. and C.-W.Q. drafted the paper with input from all authors.

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Correspondence to Kai Wang, Peixiang Lu or Cheng-Wei Qiu.

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Hu, G., Hong, X., Wang, K. et al. Coherent steering of nonlinear chiral valley photons with a synthetic Au–WS2 metasurface. Nat. Photonics 13, 467–472 (2019). https://doi.org/10.1038/s41566-019-0399-1

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