Abstract-Giant Terahertz-Wave Absorption by Monolayer Graphene in a Total Internal Reflection Geometry

Yoichi Harada, Muhammad Shoufie Ukhtary, Minjie Wang, Sanjay K. Srinivasan, Eddwi H. Hasdeo, Ahmad R.T. Nugraha, G. Timothy Noe, Yuji Sakai, Robert Vajtai, Pulickel M Ajayan, Riichiro Saito, and Junichiro Kono

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00663

Publication Date (Web): December 12, 2016

Copyright © 2016 American Chemical Society

http://pubsdc3.acs.org/doi/abs/10.1021/acsphotonics.6b00663

We experimentally demonstrated significant enhancement of terahertz-wave absorption in monolayer graphene by simply sandwiching monolayer graphene between two dielectric media in a total internal reflection geometry. In going through this structure, the evanescent wave of the incident terahertz beam interacts with the sandwiched graphene layer multiple (up to four) times at varying incidence angles. We observed extremely large attenuation (up to ~70% per reflection), especially for s-polarized radiation. The experimental results are quantitatively consistent with our calculations, where we modeled the experiment as an electromagnetic wave reflection process in monolayer graphene. We also derived analytical expressions for the absorptance, showing that the absorptance is proportional to the amount of Joule heating on the graphene surface induced by the terahertz radiation.

Abstract-High-Contrast Terahertz Wave Modulation by Gated Graphene Enhanced by Extraordinary Transmission through Ring Apertures

Weilu Gao , Jie Shu , Kimberly Reichel , Daniel V. Nickel , Xiaowei He , Gang Shi , Robert Vajtai ,Pulickel M Ajayan , Junichiro Kono , Daniel M. Mittleman , and Qianfan Xu

Nano Lett., Just Accepted Manuscript

DOI: 10.1021/nl4041274

Publication Date (Web): February 3, 2014

Copyright © 2014 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/nl4041274

Gate-controllable transmission of terahertz (THz) radiation makes graphene a promising material for making high-speed THz wave modulators. However, to date, graphene-based THz modulators have exhibited only small on/off ratios due to small THz absorption in single-layer graphene. Here we demonstrate a ~50% amplitude modulation of THz waves with gated single-layer graphene by the use of extraordinary transmission through metallic ring apertures placed right above the graphene layer. The extraordinary transmission induced ~7 times near-filed enhancement of THz absorption in graphene. These results promise CMOS-compatible THz modulators with tailored operation frequencies, large on/off ratios, and high speeds, ideal for applications in THz communications, imaging, and sensing.