Improvement And Simulation Of Dispersive HIE-FDTD Method In Graphene Absorber

Graphene has zero band gap structure,low loss and dynamic adjustability,which has high practical value in the application of terahertz absorbers.Finite difference time domain(FDTD)method combined with assisted difference(ADE)method has been applied to the simulation analysis of graphene absorber in terahertz band,but this method requires a very small mesh to divide the graphene region,which leads to its low calculation efficiency for the graphene absorber.Therefore,it is very important to improve the computing efficiency.In this thesis,based on the analysis of graphene-related theories and the stability conditions of the Hybrid Explicit Implicit Finite Difference Time Domain(HIE-FDTD)method,uses the ADE method to introduce the in-band conductivity of the terahertz band graphene into the HIE-FDTD method.In this way,the iterative formula of the dispersion HIE-FDTD method in graphene is obtained,and the stability conditions of the method,the CPML absorption boundary,the total field/scattering field boundary and the periodic boundary are derived in detail.In the numerical simulation,the high efficiency of the dispersive HIE-FDTD method is verified through the infinite graphene structure.The results show that this method is faster than FDTD method in the simulation of graphene.For graphene with a curved structure,the conformal technology is introduced into the dispersive HIE-FDTD method to form an improved dispersive HIE-FDTD method,and the improved dispersive HIE-FDTD method and the dispersive HIE-FDTD method are used for the curved structure respectively.Graphene is simulated.The simulation results show that the calculation speed of the improved chromatic dispersion HIE-FDTD method is 5 times higher than that of the chromatic dispersion HIE-FDTD under the condition of maintaining the same calculation accuracy.Finally,the graphene single-band and dual-band terahertz absorbers are designed,and the improved dispersion HIE-FDTD method is used to simulate and analyze them.The simulation results show that the single-band graphene absorber has an absorption rate of 99.8%for incident waves near 2.68 THz.The absorption rate of the double-band graphene absorber to the incident wave is greater than 96%near 1.66 THz and 3.25 THz.The above results show that the designed absorber achieves an ideal absorption effect on the incident wave,and this structure has a certain reference value.