Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-751, Republic of Korea.
Nat Mater. 2012 Nov;11(11):936-41. doi: 10.1038/nmat3433. Epub 2012 Sep 30.
The extraordinary electronic properties of graphene provided the main thrusts for the rapid advance of graphene electronics. 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 plasmonics. 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 metamaterial, 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 metamaterial. 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.
石墨烯非凡的电子特性为石墨烯电子学的快速发展提供了主要动力。在光子学中，石墨烯的栅极可控电子特性为有效地控制光子与石墨烯的相互作用提供了一种途径，这最近激发了人们对石墨烯等离子体学的浓厚兴趣。然而，由于其非共振 Drude 型行为，未经图案化的石墨烯本身的电光调谐能力对于实际的光电应用来说仍然不够强。在这里，我们证明了在二维超材料中可以实现大量的栅极诱导的太赫兹波的持续开关和线性调制，其中集成了原子级薄的栅控二维石墨烯层。超材料的强共振可以大大增强石墨烯层中的栅控光物质相互作用。尽管嵌入的单层石墨烯的厚度比波长小六个数量级以上（<λ/1,000,000），但单层厚度与超材料结合可以在室温下将透射波的幅度调制高达 47%，并将其相位调制 32.2°。更有趣的是，栅控有源石墨烯超材料在太赫兹波的传输中表现出滞后行为，这表明存在持久的光子记忆效应。
