Research On Broadband Perfect Absorption In Dielectric-Loaded Graphene

Graphene has a tunable electromagnetic response capability in the ultra-broad frequency range from terahertz to ultraviolet,thus it has a good application prospect in the tunable electromagnetic wave absorber.Since the discovery of graphene,a mass of graphene-based absorption structures working from terahertz to ultraviolet region have been proposed.The working bandwidth of these absorbers can be classified into narrowband and broadband.As for the structure feature,these absorbers are based on either nonstructured or micro/nano-structured graphene.In this thesis,we focus on the broadband graphene absorber based on nonstructured graphene.The main research contents and results of this thesis are as follows:1.The graphene absorber loaded with dielectric with gradient in-plane width was proposed and designed,and its novel absorption mechanism was revealed: multi-band continuous plasmon resonance,and the effects of structural parameters of the dielectric with gradient in-plane width,incident angle and Fermi level on the absorption were studied.The results show that the absorption structure can achieve broadband near-perfect absorption with a relative bandwidth of 65%(absorptivity> 90%).2.The graphene absorber loaded with dielectric with gradient vertical width was proposed and designed,and its unique absorption mechanism was revealed: the coupling between Mie resonance and graphene plasmons promotes the broadening of the Mie resonance,and increases the absorptivity and the absorption bandwidth of graphene simultaneously.The result shows that the relative bandwidth of over 99% absorption of this structure can reach 60%.