Abstract-Observation of Gate-Tunable Coherent Perfect Absorption of Terahertz Radiation in Graphene

Nurbek KakenovOsman BalciTaylan TakanVedat Ali OzkanHakan AltanCoskun Kocabas



https://figshare.com/articles/Observation_of_Gate-Tunable_Coherent_Perfect_Absorption_of_Terahertz_Radiation_in_Graphene/3497729

Abstract-We report experimental observation of electrically tunable coherent perfect absorption (CPA) of terahertz (THz) radiation in graphene. We develop a reflection-type tunable THz cavity formed by a large-area graphene layer, a metallic reflective electrode, and an electrolytic medium in between. Ionic gating in the THz cavity allows us to tune the Fermi energy of graphene up to 1 eV and to achieve a critical coupling condition at 2.8 THz with absorption of 99%. With the enhanced THz absorption, we were able to measure the Fermi energy dependence of the transport scattering time of highly doped graphene. Furthermore, we demonstrate flexible active THz surfaces that yield large modulation in the THz reflectivity with low insertion losses. We anticipate that the gate-tunable CPA will lead to efficient active THz optoelectronics applications.

Abstract-Gate-tunable coherent perfect absorption of terahertz radiation in graphene

Fangli Liu, Y.D. Chong, Shaffique Adam, Marco Polini

(Submitted on 11 Feb 2014)

http://arxiv.org/abs/1402.2368

Perfect absorption of radiation in a graphene sheet may play a pivotal role in the realization of technologically relevant optoelectronic devices. In particular, perfect absorption of radiation in the terahertz (THz) spectral range would tremendously boost the potential of graphene in this difficult range of photon energies, which still lacks cheap and robust devices operating at room temperature. In this work we demonstrate that unpatterned graphene flakes deposited on back-gated devices can display gate-tunable coherent perfect absorption (CPA) in the THz spectral range. We present theoretical estimates for the CPA operating frequency as a function of doping, which take into account the presence of common sources of disorder in graphene samples.