Yada Kyohei, Shimojo Takashi, Okada Hideyuki, Sakurai Atsushi
Graduate School of Science and Technology, Niigata University, 8050, Ikarashi 2-no-cho, Niigata 950-2181, Japan.
Department of Mechanical and Production Engineering, Niigata University, 8050, Ikarashi 2-no-cho, Niigata 950-2181, Japan.
Sensors (Basel). 2021 Oct 11;21(20):6738. doi: 10.3390/s21206738.
Components smaller than the wavelength of electromagnetic waves are called meta-atoms. Thermal emission can be controlled by an artificial structure in which these meta-atoms are arranged on the surface. This artificial structure is called a metasurface, and its optical properties are determined by the materials and shapes of the meta-atoms. However, optical devices may require active control of thermal emission. In the present study, we theoretically and numerically analyze a wavelength-selective emitter using a graphene ribbon metasurface. The graphene ribbon metasurface consists of a graphene ribbon array, potassium bromide thin film, and silver substrate. The geometric parameters of the graphene metasurface are determined based on an equivalent circuit model that agrees well with the results of the electromagnetic field analysis (rigorous coupled-wave analysis). The proposed emitter causes impedance matching depending on the conductivity of the graphene ribbon in a very narrow wavelength range. The conductivity of graphene can be actively controlled by the gate voltage. Therefore, the proposed emitters may realize near-perfect emission with a high quality factor and active controllable switching for various wavelengths. In addition, the quality factor can be changed by adjusting the electron mobility of graphene. The proposed emitter can be used for optical devices such as thermophotovoltaic systems and biosensing.
小于电磁波波长的组件被称为超原子。热发射可以通过一种人工结构来控制，在这种结构中，这些超原子排列在表面。这种人工结构被称为超表面，其光学特性由超原子的材料和形状决定。然而，光学器件可能需要对热发射进行主动控制。在本研究中，我们对使用石墨烯带超表面的波长选择性发射器进行了理论和数值分析。石墨烯带超表面由石墨烯带阵列、溴化钾薄膜和银衬底组成。石墨烯超表面的几何参数是基于一个等效电路模型确定的，该模型与电磁场分析（严格耦合波分析）的结果吻合良好。所提出的发射器在非常窄的波长范围内根据石墨烯带的电导率实现阻抗匹配。石墨烯的电导率可以通过栅极电压进行主动控制。因此，所提出的发射器可以实现具有高品质因数的近乎完美的发射，以及针对各种波长的主动可控切换。此外，品质因数可以通过调整石墨烯的电子迁移率来改变。所提出的发射器可用于诸如热光伏系统和生物传感等光学器件。
