Abstract
Graphene is a two-dimensional material with exotic electronic, optical and thermal properties. The optical absorption in monolayer graphene is limited by the fine structure constant α. Here we demonstrated the strong enhancement of light absorption and thermal radiation in homogeneous graphene. Numerical simulations show that the light absorbance can be controlled from near zero to 100% by tuning the Fermi energy. Moreover, a set of periodically located absorption peaks is observed at near grazing incidence. Based on this unique property, highly directive comb-like thermal radiation at near-infrared frequencies is demonstrated.
Highlights
As one-atom thick carbon material described by a two-dimensional (2D) Dirac-like equation, graphene has attracted much attention in recent years with respect to its extraordinary electronic and optical properties such as ballistic transport and saturable absorption [1,2,3,4]
At lower frequencies, the property of graphene is mainly determined by the intraband transition which is similar to the case of Drude-type material [7, 8]
One of the most crucial aspects of graphene is that it is optically tunable via electrostatic doping, that means, the plasmon frequency of graphene can be tuned by the chemical potential μc or Fermi energy EF [10,11,12,13,14]
Summary
As one-atom thick carbon material described by a two-dimensional (2D) Dirac-like equation, graphene has attracted much attention in recent years with respect to its extraordinary electronic and optical properties such as ballistic transport and saturable absorption [1,2,3,4]. Based on the electric tunable optical properties of graphene, various applications have been proposed by different groups. Researchers demonstrated that total absorption of light can be achieved by utilizing periodically patterned graphene [15,16,17]. One should note that similar absorption enhancement effect in metamaterial has already demonstrated by many groups [18,19,20,21]. The spectral and spatial control of thermal radiation in graphene system has rarely been investigated it has been used to extract the temperature distribution and spatial location of the Dirac point in the graphene channel [30]. Based on Kirchhoff’s law, the passive and active tuning of directive thermal radiation in the near-infrared frequencies is demonstrated
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