Graphene is a promising candidate for broadband and high-speed photodetectors. Nevertheless, the weak optical absorption of graphene restricts the performance of graphene photodetectors. In this work, the integration of a graphene photodetector with plasmonic metasurface which consists of optical nanoantennas is theoretically and numerically investigated. Also, the suggested photodetector is analytically evaluated via transfer matrix model (TMM). The incorporation of plasmonic modified omega-shaped nanoantennas not only boosts the light-graphene interactions but also it reinforces the light absorption, remarkably. The suggested optical nanoantennas contribute to the near-field enhancement and increased optical performance of the photodetector in two ways. First, by employing the proposed nanoantennas, electric quadrupole and vertical dipole plasmon oscillations are excited which enhance the magnetic fields around the nanoantennas. Second, due to the excitation of localized surface plasmon resonances (LSPRs), electric fields are highly concentrated and confined in the nanoscale regions, nanogaps and edges of nanoantennas. Similarly, electric fields are also highly enhanced in the ring sections of the nanoantennas, located parallel to the incident light. The proposed photodetector has small footprint and its broadband and tunable absorption can be tailored by manipulating the geometrical parameters of the structure and chemical potential of graphene. A near-unity absorption peak with FWHM of 343 nm is obtained at the telecommunication wavelength of 1550 nm. Also, absorbed power in the graphene increases to 66% and an ultrahigh electric field enhancement of 1350 is achieved in the gaps of the nanoantenna. The proposed photodetector can have possible applications in the nano-biosensing, imaging, biomedical monitoring and optical communication systems.

石墨烯是宽带和高速光电探测器的有前途的候选者。然而，石墨烯的弱光吸收限制了石墨烯光电探测器的性能。在这项工作中，从理论上和数值上研究了石墨烯光电探测器与由光学纳米天线组成的等离子体超表面的集成。此外，建议的光电探测器通过传递矩阵模型 (TMM) 进行分析评估。等离子体修饰的 omega 形纳米天线的结合不仅增强了光-石墨烯的相互作用，而且还显着增强了光吸收。建议的光学纳米天线以两种方式有助于近场增强和光电探测器光学性能的提高。首先，通过使用所提出的纳米天线，电四极子和垂直偶极子等离子体振荡被激发，增强了纳米天线周围的磁场。其次，由于局部表面等离子体共振（LSPR）的激发，电场高度集中并限制在纳米级区域、纳米间隙和纳米天线的边缘。同样，在平行于入射光的纳米天线的环形部分中，电场也得到了高度增强。所提出的光电探测器占地面积小，其宽带和可调吸收可以通过操纵石墨烯的结构和化学势的几何参数来定制。在 1550 nm 的电信波长处获得了 FWHM 为 343 nm 的近统一吸收峰。还，石墨烯中的吸收功率增加到 66%，并且在纳米天线的间隙中实现了 1350 的超高电场增强。所提出的光电探测器在纳米生物传感、成像、生物医学监测和光通信系统中具有可能的应用。