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Electrical control of second-harmonic generation in a WSe2 monolayer transistor

Nature Nanotechnology volume 10, pages 407–411 (2015)Cite this article

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Abstract

Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies1, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to such phenomena are often challenging to tune in a given material and, so far, dynamical control of optical nonlinearities remains confined to research laboratories as a spectroscopic tool2. Here, we report a mechanism to electrically control second-order optical nonlinearities in monolayer WSe2, an atomically thin semiconductor. We show that the intensity of second-harmonic generation at the A-exciton resonance is tunable by over an order of magnitude at low temperature and nearly a factor of four at room temperature through electrostatic doping in a field-effect transistor. Such tunability arises from the strong exciton charging effects in monolayer semiconductors3,4, which allow for exceptional control over the oscillator strengths at the exciton and trion resonances. The exciton-enhanced second-harmonic generation is counter-circularly polarized to the excitation laser due to the combination of the two-photon and one-photon valley selection rules5,6,7,8, which have opposite helicity in the monolayer. Our study paves the way towards a new platform for chip-scale, electrically tunable nonlinear optical devices based on two-dimensional semiconductors.

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Figure 1: Characterization of second-harmonic generation in monolayer WSe2 transistor.
Figure 2: Resonant enhancement and gate tunability of room-temperature SHG.
Figure 3: Electrical control of photoluminescence and SHG at 30 K.
Figure 4: Valley-dependent SHG selection rules.

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Acknowledgements

This work was mainly supported by the Department of Energy Office of Basic Energy Sciences (DoE BES, DE-SC0008145 and SC0012509). Device fabrication was partially supported by the National Science Foundation (NSF, DMR-1150719). P.G. and W.Y. were supported by the Research Grant Council (HKU705513P and HKU9/CRF/13G) and University Grant Council (AoE/P-04/08) of the government of Hong Kong, and the Croucher Foundation under the Croucher Innovation Award. J.Y. and D.M. were supported by the US DoE, BES, the Materials Sciences and Engineering Division. X.X. acknowledges support from the Cottrell Scholar Award, and S.W. acknowledges support from the State of Washington funded Clean Energy Institute. Device fabrication was performed at the Washington Nanofabrication Facility and NSF-funded Nanotech User Facility.

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Authors and Affiliations

  1. Department of Physics, University of Washington, Seattle, 98195, Washington, USA

    Kyle L. Seyler, John R. Schaibley, Pasqual Rivera, Aaron M. Jones, Sanfeng Wu & Xiaodong Xu

  2. Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China

    Pu Gong & Wang Yao

  3. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, 37831, Tennessee, USA

    Jiaqiang Yan & David G. Mandrus

  4. Department of Materials Science and Engineering, University of Tennessee, Knoxville, 37996, Tennessee, USA

    Jiaqiang Yan & David G. Mandrus

  5. Department of Physics and Astronomy, University of Tennessee, Knoxville, 37996, Tennessee, USA

    David G. Mandrus

  6. Department of Materials Science and Engineering, University of Washington, Seattle, 98195, Washington, USA

    Xiaodong Xu

Authors
  1. Kyle L. Seyler
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Contributions

X.X. conceived the idea. K.L.S. designed the experiment and performed the measurements, assisted by J.R.S., A.M.J., and P.R. P.R. and K.L.S. fabricated the devices. J.Y. and D.M. synthesized and characterized the bulk WSe2 crystal. K.L.S. performed data analysis, with input from P.G., J.R.S., S.W., X.X. and W.Y. K.L.S. wrote the manuscript, assisted by X.X., J.R.S. and W.Y. All authors discussed the results and commented on the manuscript.

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Correspondence to Xiaodong Xu.

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Seyler, K., Schaibley, J., Gong, P. et al. Electrical control of second-harmonic generation in a WSe2 monolayer transistor. Nature Nanotech 10, 407–411 (2015). https://doi.org/10.1038/nnano.2015.73

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