Abstract-Tunable terahertz reflection of graphene via ionic liquid gating

Yang Wu1,2,3, Xuepeng Qiu1, Hongwei Liu3, Jingbo Liu4, Yuanfu Chen4, Lin Ke3 and 
Hyunsoo Yang1,2

http://iopscience.iop.org/article/10.1088/1361-6528/aa57ad

We report a highly efficient tunable THz reflector in graphene. By applying a small gate voltage (up to ±3 V), the reflectance of graphene is modulated from a minimum of 0.79% to a maximum of 33.4% using graphene/ionic liquid structures at room temperature, and the reflection tuning is uniform within a wide spectral range (0.1–1.5 THz). Our observation is explained by the Drude model, which describes the THz wave-induced intraband transition in graphene. This tunable reflectance of graphene may contribute to broadband THz mirrors, deformable THz mirrors, variable THz beam splitters and other optical components.

Abstract-Graphene Terahertz Modulators by Ionic Liquid Gating

1. Yang Wu^1,2, 
2. Chan La-o-vorakiat^3,4,
3. Xuepeng Qiu⁵, 
4. Jingbo Liu⁶, 
5. Praveen Deorani⁵, 
6. Karan Banerjee⁵, 
7. Jaesung Son⁵, 
8. Yuanfu Chen⁶, 
9. Elbert E. M. Chia^4,*and
10. Hyunsoo Yang^1,2,*

Article first published online: 3 FEB 2015

http://onlinelibrary.wiley.com/doi/10.1002/adma.201405251/abstract;jsessionid=4D3B95BDF171BDBF815E1504D6336819.f03t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false

DOI: 10.1002/adma.201405251

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Excellent-performance terahertz (THz) modulators based on graphene/ionic liquid/graphene sandwich structures are demonstrated. The modulation covers a broadband frequency range from 0.1 to 2.5 THz with a modulation depth of up to 99% by applying a small gate voltage of 3 V. The outstanding performance of the proposed devices is due to the conical band structure of the graphene and the powerful gating effect of the ionic liquid in proximity to the graphene.