Broadband Perfect Absorption Of Layered Structure With Graphene Metamaterial

Since the graphene has been proved to be able to exist stably in nature,it has gained broad attention from the researchers because of its special structure and excellent performances.Particularly,the graphene can invoke surface mode in Terahertz range.It makes the graphene a capable candidate for Terahertz absorber manufacture.Traditional optical device can hardly get response in Terahertz range because of the special properties of Terahertz.A series of studies have shown that man-made metamaterial have a better absorption performance in Terahertz with the oscillation of the carriers on the surface of the conductive films.It is meaningful for optics and electromagnetics researches.Besides,the graphene has a better absorption performance in Terahertz range compare to ordinary metal.This makes the research on metamaterials based on graphene a hot-spot in electromagnetics.This dissertation includes the theory research and design of the electromagnetic absorption based on graphene metamaterial.The main contents are listed as follows:1.An absorber based on graphene metamaterial cascaded structure has been presented.The graphene metamaterial slab is based on the design of Igor.The bandwidth is extended by cascading several slabs together.Those slabs have different prefect absorption bands,at a fixed incident angle ?/4.The width of the air gap between two different material slabs is also properly designed.The results show that the wavelength for perfect absorption has been obviously extended when 5 metamaterial slabs are placed.The results are also verified by COMSOL simulation software.The cascaded structure is only considered up to 5 layers,in order to minimize the scale of the device.When the incident wavelength is fixed at 4.35?m,the cascaded structure of different graphene metamaterial slabs(non-perfect absorption)is also investigated.By properly designing,it will still achieve the absorptance over 0.8 in a wide incident angle range from-67° to 67°.2.An absorber based on graphene metamaterial composite structure has been presented.The structure is composed by graphene metamaterial in the upper layer,air in the middle layer and metal(sliver)reflector in the lower layer.The structural parameters are properly chosen according to the influence of metamaterial parameters on electromagnetic absorption.The simulation result shows that the absorptance reaches over 0.8 at incident angle ?/4 and within incident wavelength range 0.1-6?m.When incident wavelength equals 3.5?m,the absorptance reaches over 0.9 in the incident angle range from-60° to 60°.The structure will achieve the bandwidth extensions in both wavelength and angle simultaneously with high absorptance.