Graphene-based photodetectors have been caught in the spotlight of optoelectronics devices and they are significant candidates for tunable detectors. Unfortunately, little reports are presented for absorption enhancement in near-infrared range. Therefore, here, a graphene-based photodetector with plasmonic structure consisting of Silicon and SiO₂ substrate, graphene layer, and metal nano-grating in near-infrared range is proposed. The optical absorption of graphene layer in this structure increases due to the occurrence of plasmonic effects and excitation of surface plasmon polaritons (SPPs) in metal and graphene interface. The optical response of the proposed structure is numerically simulated using the finite-difference time-domain (FDTD) method. To optimize the optical absorption of the structure, the effects of geometrical parameters, the chemical potential of graphene, the number of graphene layers, and the incident angle have been investigated. Based on numerical results, the absorption of monolayer graphene enhanced from 0.023 to nearly 0.70, even to a maximum value of 0.80 in three-layer graphene and the total absorption of optimized structure reached to about 0.98 at telecommunication wavelength (1.55 $\mathrm{\mu }$m). Moreover, the absorption spectrum of the proposed structure can be tuned by either changing the geometrical parameters of nano-grating or chemical potential of graphene.

基于石墨烯的光电探测器已成为光电设备的关注焦点，它们是可调探测器的重要候选产品。不幸的是，几乎没有关于提高近红外吸收率的报道。因此，这里，具有由硅和SiO ₂组成的等离子体结构的石墨烯基光电探测器提出了近红外衬底，石墨烯层和金属纳米光栅。由于金属和石墨烯界面中的等离子体效应和表面等离激元极化子（SPPs）的激发，该结构中石墨烯层的光吸收增加。使用有限差分时域（FDTD）方法对拟议结构的光学响应进行了数值模拟。为了优化结构的光学吸收，研究了几何参数，石墨烯的化学势，石墨烯层数和入射角的影响。根据数值结果，单层石墨烯的吸收率从0.023提高到接近0.70，甚至在三层石墨烯中达到最大值0.80，优化结构的总吸收率达到约0。$\mathrm{\mu }$m）。此外，可以通过改变纳米光栅的几何参数或石墨烯的化学势来调节所提出结构的吸收光谱。