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Switching terahertz waves with gate-controlled active graphene metamaterials


The extraordinary electronic properties of graphene provided the main thrusts for the rapid advance of graphene electronics1. In photonics, the gate-controllable electronic properties of graphene provide a route to efficiently manipulate the interaction of photons with graphene, which has recently sparked keen interest in graphene plasmonics2,3,4,5,6,7,8,9,10. However, the electro-optic tuning capability of unpatterned graphene alone is still not strong enough for practical optoelectronic applications owing to its non-resonant Drude-like behaviour. Here, we demonstrate that substantial gate-induced persistent switching and linear modulation of terahertz waves can be achieved in a two-dimensional metamaterial11,12, into which an atomically thin, gated two-dimensional graphene layer is integrated. The gate-controllable light–matter interaction in the graphene layer can be greatly enhanced by the strong resonances of the metamaterial13. Although the thickness of the embedded single-layer graphene is more than six orders of magnitude smaller than the wavelength (<λ/1,000,000), the one-atom-thick layer, in conjunction with the metamaterial, can modulate both the amplitude of the transmitted wave by up to 47% and its phase by 32.2° at room temperature. More interestingly, the gate-controlled active graphene metamaterials show hysteretic behaviour in the transmission of terahertz waves, which is indicative of persistent photonic memory effects.

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Figure 1: Schematic view and device images of gate-controlled active graphene metamaterials.
Figure 2: Gate-controlled amplitude and phase changes of terahertz waves transmitted through the hexagonal graphene metamaterials.
Figure 3: Gate-controlled amplitude change of terahertz waves transmitted through the aDSR graphene metamaterials.
Figure 4: Electrically controlled photonic memory operation with the gate-controlled active graphene metamaterials.


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We thank B. H. Hong for the discussion on the application of graphene, Y-J. Yu for the discussion on carrier transport in graphene, J. H. Han for the characterization of graphene, and H. Choi for proofreading the manuscript. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2008-0062235, 2009-0069459, 2010-0012058, 2011-0020186 and 2011-0028151). S.S.L. acknowledges the support by the NRF of Korea grant funded by the MEST (No.2010-0027050). S-Y.C. acknowledges the GFR Program (2011-0031640) sponsored by the MEST. C-G.C. acknowledges the Nano R&D Program (2011-0019169) through the NRF of Korea funded by the MEST and the Creative Research Program of the ETRI (11YF1110). X.Z. acknowledges the support from the US Department of Energy under contract no. DE-AC02-05CH11231 through Materials Sciences Division of Lawrence Berkeley National Laboratory (LBNL).

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S.H.L., M.C., T-T.K. and B.M. conceived the original idea. S.H.L. and M.C. fabricated the samples. T-T.K., S.H.L. and M.C. performed the experiments. S.H.L., M.C., S.L., M.L., H.K.C., C-G.C., S-Y.C. and B.M. characterized the graphene. S.H.L., M.C., T-T.K., S.L., M.L., X.Y., S.S.L., S-Y.C., X.Z. and B.M. analysed the data and discussed the results. S.H.L., M.C., T-T.K., S.L., M.L., X.Z. and B.M. wrote the paper, and all authors provided feedback.

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Correspondence to Bumki Min.

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Lee, S., Choi, M., Kim, TT. et al. Switching terahertz waves with gate-controlled active graphene metamaterials. Nature Mater 11, 936–941 (2012).

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