Theoretical And Experimental Research On Monolayer-graphene-based Perfect Absorption Structures In The Near Infrared

In recent years,graphene has attracted extensive concern in many fields due to its excellent properties.Graphene has the ultra-broad spectrum response,ultrafast response,the ultrahigh carrier mobility,and its surface conductance can be tuned by electrical and chemical doping,which make graphene an ideal material in optoelectronic fields.However,the absorption of graphene towards the incident light is too low because of its thin thickness,which strictly limits the applications of graphene in the photoelectric devices.Therefore,it is a critical problem to improve the absorption rate of graphene.This work mainly focus on enhancing absorption of graphene by coupling graphene with periodical resonant structures in the near infrared and achieving total absorption of monolayer-graphene-based structures towards incident light.The main works of the thesis are summarized as follows:1.Design and fabricate perfect absorption structures by coupling graphene with two-dimension dielectric periodical structures backed by a metal mirror.The proposed structure can achieve total absorption toward incident light at 1526.5nm with full width at half maximum about 18 nm in simulation,and the peak absorption rate of graphene reaches 91.9%.In the experiments,peak absorption of 99.4% is measured for a fabricated structure,and the measured absorption spectra of fabricated strucutres agree well with the simulation results.2.Design a monolayer-graphene-based perfect absorption structure with assistant of a multilayer dielectric mirror instead of the metal mirror,and total absorption of the graphene layer is achieved.3.Design absorption structures with broad absorption bands by coupling graphene with one-dimension asymmetrical dielectric grating and gratings with different thicknesses.4.Utilizing magnetic dipole resonance to design perfect absorption structures by coupling graphene with metal periodical structures.The peak absorption of the proposed structure around 1550 nm approaches 100% and the full width at half maximum is over 150 nm.5.Utilizing magnetic coupling effects to design perfect absorption structures by coupling graphene with deep sub-wavelength metal periodical structures.The peak absorption of the proposed structure nears 100% at the telecommunication band,where 74% absorption is attributed to graphene.The resonant wavelength and absorption rate can keep stable in a large range of the incident angle.