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Observation of Gate-Tunable Coherent Perfect Absorption of Terahertz Radiation in Graphene
journal contribution
posted on 2016-07-25, 12:21 authored by Nurbek Kakenov, Osman Balci, Taylan Takan, Vedat Ali Ozkan, Hakan Altan, Coskun KocabasWe 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.