Optics and Photonics Society of Iran

 Employing graphene in optical photo detectors is very promising due to the unique features of graphene such as fast dynamic of carriers and wavelength independent absorption. However, the low absorption of graphene has a negative impact on the photo detection characteristics. In this article, a mid-Infrared photo detector based on single layer graphene is designed and simulated which incorporates metallic Nano-antennas to enhance the absorption and hence the photo-detector response. In these structures, plasmonic effects are responsible for the enhanced absorption by severely increasing the electric field magnitude at the metal-graphene interface. In this article, it is shown that by a slight modification in the nanostructure design, it is possible to shift the peak absorption wavelength between 4 to 6mm. The impact of the graphene chemical potential on the absorption strength is also discussed. In brief, maximum absorption of the designed photo detector for 4.6mm and 5.5mm are calculated to be 9% and 12% respectively. Moreover, it is shown that by addition of another layer of graphene, it is possible to increase the absorption at the wavelength at l=4.6mm to nearly 14%.