Gate-tunable nearly total absorption in graphene with resonant metal back reflector

¹ Nanoscale Science and Technology Laboratory, Institate for Advanced Study, Nanchang University Nanchang 330031, China
² Department of Physics, Nanchang University - Nanchang 330031, China
³ Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences Hefei 230031, China

^(a) jtliu@semi.ac.cn
^(b) fhsu@issp.ac.cn

Received: 26 November 2013
Accepted: 4 December 2013

Abstract

The gate-tunable absorption of graphene layers with a resonant metal back reflector (RMBF) is theoretically investigated. We demonstrate that the absorption of graphene with RMBF can vary from nearly negligible to nearly total by tuning the external gate voltage within the terahertz (THz) spectra range. Total THz absorption is less affected by the incident angle of THz beams. This peculiar nearly total THz absorption can be attributed to the Fabry-Perot cavity effect, which enhances the absorption and reduces the reflection of graphene. The absorption spectra of the graphene-RMBF structure can also be tailored in bandwidth and center frequency by changing the thickness and dielectric constant of the spacer layer. These findings can lead to the development of tunable THz photonic devices and have potential applications in studies on the ultrafast dynamics of Dirac fermions in graphene.