| Graphene has been widely concerned since it was stripped by researchers in Geim and Novoselov in 2004 by mechanical stripping.Graphene is a single-layer carbon atom two-dimensional material with a hexagonal honeycomb structure existing in nature.It has excellent optical and electrical properties and can be used in nanoelectronic devices and optoelectronic devices.Compared with other two-dimensional materials,graphene has some unique properties,such as its carrier concentration can be adjusted by external bias voltage or chemical doping,making it have good tunable characteristics.Surface plasmon is an electromagnetic oscillation formed by the interaction of free electrons and photons in the surface area of a metal.Surface plasmons under a specific frequency of incident photons,strong absorption or scattering will occurs on the structure surface,and then the electromagnetic field will be focused to the range of the sub-wavelength scale,resulting in the local electric field enhancement,which enhances the interaction between light and matter.In addition,surface plasmons can also break through the diffraction limit,providing the possibility for the development of micron and nanoscale electronic components.The combination of surface plasmons and artificially designed materials?metamaterials?,that is,surface plasmons metamaterials,has stimulated the research upsurge of scientific researchers and is one of the hotspots in modern optics.Based on graphene surface plasmons metamaterials,this paper studies three kinds of graphene composite structure absorbers through theoretical design and simulation calculation.Using the finite-difference time-domain method,the light absorption properties of graphene-based structures are discussed and analyzed.The main research contents of this paper are as follows:?1?A surface plasmon absorber based on a dumbbell-shaped graphene metamaterial array is proposed.The absorber is composed of a top-layer dumbbell shaped graphene metamaterial array,a silicon dioxide insulator material in the middle layer and a semiconductor silicon material in the bottom layer.The simulation results show that the absorption characteristics of graphene can be changed by changing the geometric parameters of graphene structure and Fermi energy level.The study found that as the angle of incidence changes,the resonance wavelength is insensitive to TM polarization.In addition,the study also found that double-layer dumbbell-shaped graphene arrays have better absorption performance than single-layer dumbbell-shaped graphene arrays.?2?A three-band metamaterial perfect absorber based on a periodically arranged graphene split ring resonator?SRR?is theoretically designed.The finite difference time domain?FDTD?method and the simulation results show that the absorber has three absorption peaks at the frequencies of 3.56 THz,10.38 THz and 12.96 THz,and the absorption efficiency is 99.57%,99.98%and 99.76%,respectively.By changing the chemical potential of graphene,the absorption characteristics of the absorber can be flexibly tunable.In addition,the sensing performance of the metamaterial absorber is also studied,and the results show that the sensing performance of high frequency band was significantly higher than that of low frequency band.?3?A graphene metamaterial absorber based on periodically arranged elliptical cylinder air hole was designed and studied,and the perfect absorption was achieved by the critical coupling theory.By increasing the thickness of SiO2?d2?and PMMA?d4?,the resonance peak wavelength of the structure is red-shifted.In addition,if the ratio of the radius of the elliptical cylinder to the period changes,the spectral position of the absorption peak also changes.By studying the refractive index of the surrounding medium,it is found that the structure has high sensing performance and quality factors,which are S=342.7 nm/RIU,FOM=199.2,and Q=664.2,which have good development potential on biosensors. |
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