Research Of The Applications Of Coupled Graphene Nanostructures

As a novel two-dimensional material,graphene exhibits extraordinary optoelectronic properties.Compared with traditional plasmonic materials such as gold and silver,graphene shows stronger confinement of local fields,significantly less loss and its plasmonic resonances can be dynamically tuned by changing the Fermi energy with chemical or electrical doping.This thesis focused on the research of surface plasmonic resonances(SPR)in coupled graphene nanostructures,and designed a reflection-type electrically tunable terahertz optical polarization converter and a tunable bulk refractive-index sensor in infrared waveband by using the SPR effects in different coupled graphene nanostructures.The main contents are summarized as follows:1.The dispersion relation model of graphene was analyzed and theoretical model of plasmonic resonance modes supported by individual and coupled graphene nanodisks were investigated.2.A reflection-type electrically tunable mid-to-far infrared optical polarization converter was proposed and designed.The numerical simulations results show that the polarization conversion rate achieves 99.7% and 99.5% at about 47 THz and 51 THz,respectively.In addition,the polarization conversion can be dynamically tuned at different frequencies via tuning the Fermi energy of graphene.The polarization conversion performance can also be controlled by varying the distance between the coupled graphene nanodisks.3.The high-order Fano resonances phenomenon in coupled graphene disk-ring nanostructure was investigated.The physical mechanism was explained by plasmon hybridization theory,and the influence of structural asymmetric offsets and different Fermi energy of graphene were studied.The numerical simulations demonstrate high refractive index sensitivities as large as ~4000nm/RIU with FOM approaching 32 when the coupled graphene disk-ring nanostructure is applied in infrared sensing.