Hayati Raad Shiva, Atlasbaf Zahra
Opt Express. 2021 May 24;29(11):17510-17521. doi: 10.1364/OE.423129.
In this paper, a bi-functional tunable reflector/absorber device using an assembly of graphene-coated cylindrical wires, backed by a thermally controlled phase change material, is proposed. The reflection coefficient of the graphene-coated wire-grating manifests multiple resonances, originating from the hybridized excitation of localized surface plasmons in the graphene shells. The first plasmonic resonance (with the order of two), in the free-standing configuration, shows tunable near-perfect reflection while the second plasmonic resonance (with the order of three), in the reflector-backed array, exhibits near-perfect absorption. Because of the metal-insulator transition in the phase change material, it is feasible to switch between these two functionalities using a VO back layer. Moreover, the high-quality factor of the absorption band (Q ∼ 128.86) is due to its Fano line shape, leading to a narrow bandwidth. Thus, the absorbing mode can be possibly used for refractive index sensing with the sensitivity of S ∼ 9000 nm/RIU (refractive index unit) and figure of merit of FOM ∼ 104 RIU. In the proposed structure, different optical, material, and geometrical parameters affect the optical response of the operating bands, offering a flexible design.
本文提出了一种双功能可调反射器/吸收器装置，该装置使用涂覆石墨烯的圆柱形金属丝组件，并由热控相变材料作为衬底。涂覆石墨烯的线栅的反射系数表现出多个共振，这源于石墨烯壳层中局域表面等离子体激元的杂化激发。在独立配置下，第一个等离子体共振（二阶）显示出可调谐的近完美反射，而在反射器背衬阵列中，第二个等离子体共振（三阶）表现出近完美吸收。由于相变材料中的金属-绝缘体转变，使用VO背层在这两种功能之间切换是可行的。此外，吸收带的高品质因数（Q ∼ 128.86）归因于其法诺线形，导致带宽较窄。因此，吸收模式有可能用于折射率传感，灵敏度为S ∼ 9000 nm/RIU（折射率单位），品质因数FOM ∼ 104 RIU。在所提出的结构中，不同的光学、材料和几何参数会影响工作波段的光学响应，提供了灵活的设计。
