Absorption Enhancement in Photodetectors Based on T-Shaped Coupled Nano-Antenna for Free-Space Optical Communications Applications

Free-space optical communication is widely regarded as the next-generation high-speed wireless communication technology, and todays many attempts are aimed to improving its performance. Design of suitable photodetectors that effectively absorb light in the optical communication wavelengths range can lead to significant improvements in FSO communication; because in the FSO systems the modulated beam is transferred in free space without any optical fiber cable, and a major limiting factor for FSO is the beam divergence, which can be solved by changing the operating wavelength to 1.55μm. So, the photodetector and its optical absorption in this wavelength plays an important role. In this study, we have designed a metal-dielectric-graphene (MDG) photo detector, employing T-shaped coupled nano-antennas, and the graphene absorption, as photo-generated carrier channel in the photodetector, under different conditions is investigated. We demonstrated that the photodetector absorption at 1.55μm wavelength reaches to 38%, approximately, and only has one peak that is very suitable for the photodetector performance.