Abstract-Perfect Extinction of Terahertz Waves in Monolayer Graphene over 2-nm-Wide Metallic Apertures

1. Hyeong-Ryeol Park¹, 
2. Seon Namgung¹,
3. Xiaoshu Chen¹, 
4. Nathan C. Lindquist²,
5. Vincenzo Giannini³, 
6. Yan Francescato³,
7. Stefan A. Maier³ and
8. Sang-Hyun Oh^1,*

Article first published online: 7 JAN 2015

http://onlinelibrary.wiley.com/doi/10.1002/adom.201400546/abstract

DOI: 10.1002/adom.201400546

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

High carrier mobility and tunability in graphene enable fundamental studies for plasmonics and various applications. Despite its versatility, however, single-layer graphene (SLG) suffers from poor coupling efficiency to electromagnetic waves, presenting a major challenge for photonic applications. Compared with visible or infrared radiation, terahertz (THz) waves exhibit higher absorption in SLG due to Drude-like intraband transitions, but the wavelength-to-SLG size mismatch becomes even more dramatic. Here, we experimentally demonstrate 99% extinction of THz wave transmission when SLG covers the openings of 2-nm-wide (≈λ/1 000 000) slits through a metal film. By resonantly coupling THz waves through annular nanogaps, the extremely localized fields lead to near-perfect extinction and strong absorption in SLG. Atomic-layer lithography is used to produce these nanometer-wide, millimeter-long gaps over an entire 4-in. wafer. Furthermore, by integrating these devices with an ionic liquid, enhanced intraband absorption in the SLG leads to 80% modulation of THz waves with an operational voltage as low as 1.5 V.