چكيده به لاتين
Graphene is a 2-D nanomaterial, which is composed of a single layer of carbon atoms organized into a hexagonal lattice .Due to its unique electrical, optical, thermal and mechanical properties, increasingly intensive research has been conducted in this area. Moreover, it has been demonstrated that graphene is one of the best materials for designing THz-wave absorbers because of its capability of surface plasmon polariton-based absorption at THz frequencies. Unfortunately, previous design methods Suffer numerical methods and trial and error that's problem makes the design process very time-consuming. For conquest this problem evidently we need analytical solution.
In section 3 for the first time, the combinational use of plasma medium and graphene sheets is theoretically proposed for stealth applications. The simultaneous use of the lossy characteristics of plasma and graphene layers in the lower and upper parts of the frequency band, respectively, results in a new type of broadband radar absorbing structures.
In section 4 by using an equivalent circuit method, a polarization-insensitive terahertz (THz) absorber based on multilayer graphene-based metasurfaces (MGBMs) is systematically designed, providing an extremely broad absorption bandwidth (BW). The proposed absorber is a compact, three-layer structure, comprising square-, cross-, and circular-shaped graphene metasurfaces embedded between three separator dielectrics The optimum MGBM absorber exhibits >90% absorbance in an extremely broad frequency band of 0.55–3.12 THz (BW 140%). The results indicate a significant BW enhancement compared with both the previous metal- and graphene-based THz absorbers, highlighting the capability of the designed MGBM absorber.
In section 5 an accurate analysis of a perfect electric conductor (PEC)–backed array of graphene ribbons (PA GR) is presented based on the well-known electromagnetic (EM) image theorem, where the induced currents are theoretically derived under a transverse-magnetic-polarized incident wave. For the first time, the proposed analysis rigorously incorporates the EM coupling effects between the PEC back plate and the subwavelength array of graphene ribbons. It is proved that the strong interaction between the PEC back plate and graphene ribbons drastically affects the results, especially y in ultra-thin PAGR structures, whereas it was neglected in the previous works. As a proof of principle, an ultra-thin graphene-assisted absorber ( 0.05λ0) exhibiting tunable absorption at the terahertz regime is theoretically designed to verify the proposed analytical scheme.
In other section same section 5 we analysis other graphene metasurfaces like array of graphene ribbon with different size, Two layer array of graphene ribbon and perfect electric conductor–backed of periodic array of graphene disk.
