In this manuscript, we propose a graphene metasurface composed of an L-shaped pattern to achieve a tunable circular dichroism under oblique incidence in the mid-infrared region. For our graphene extrinsically 3D-chiral structure, there are two graphene localized surface plasmons resonant modes at the wavelength of 11.05 and 16.69 μm. A broad bandwidth circular dichroism between the two modes is generated, so are two bands of negative circular dichroism (circular dichroism is minus). The circular dichroism can be enhanced by increasing the incident angle. Maximal circular dichroism can reach 24.64% when the incident angle is 60. The mechanism of circular dichroism generation is attributed to the strong interaction between electric and magnetic dipoles. Besides, the circular dichroism can be tuned by changing the Fermi energy and is affected by the intrinsic relaxation time. It will have a wide application in photonic devices, which can promote the development of analytical chemistry and numerous other areas.

在这份手稿中，我们提出了一个由L形图案组成的石墨烯超表面，以在中红外区域的斜入射下实现可调的圆二色性。对于我们的石墨烯外在3D-手性结构中，有两个本地化的石墨烯的表面等离子体共振模式在11.05和16.69的波长μ米 两种模式之间会产生一个宽带宽的圆二色性，因此也会产生两个带负圆二色性的谱带（圆二色性为负）。圆二色性可以通过增加入射角来增强。当入射角为60°时，最大圆二色性可达24.64％。圆二色性的产生机理归因于电偶极与磁偶极之间的强相互作用。此外，圆二色性可以通过改变费米能量来调节，并受固有弛豫时间的影响。它将在光子器件中得到广泛的应用，这可以促进分析化学和许多其他领域的发展。