Research On Broadband Absorber Based On Nanowire Metamaterials

In recent years,as a new type of super high electromagnetic wave absorbing device,metamaterial absorber has attracted the attention of more and more researchers.Most conventional absorber use the grid reference line structure,and the structure only plays a role to TE wave at higher absorption efficiency.The structure of the general volume is large,to some extent,which limit its application in real life.In this paper,we present a kind of wide-band absorber based on metal nanowires,which has the advantages of higher absorption efficiency and less sensitive to the input wave polarization than the traditional absorber.In addition,the structure has the advantages of smaller size,simpler design,wider absorption spectrum and so on.The structure is composed of metal nanowires embedded in silica and backed up by a thick gold plate,which can realize near perfect absorption in ultraviolet and visible light regime and with polarization insensitive characteristics.Compared with horizontal metal/ dielectric/metal three layer sandwich structure,this structure usually can easily achieve much wider absorption bands.The main contents of this paper are as follows:1 The development trend of the metamaterial absorber are introduced,and the design method and the absorption spectrum are analyzed.2 Introducing fundamental theory of the proposed structure,including the finite difference time domain(FDTD)algorithm and its conditions,the effective medium theory,the impedance matching theory and optical mode dispersion diagram of principle,which contributes to the structural analysis of the absorption effect.3 We design a metal nanowire array structure,and a detailed analysis of the structural parameters such as the height and radius of metal nanowires on the absorption spectrum.Three different metals(gold,silver,copper)on material properties are using to research their affect on the absorption effect.At the same time,the semiconductor nanowire arrays are simply analyzed.Finally,the effect of the resonance between adjacent nanowires on the performance of the absorber is verified by simulation.4 It is found that the resonance between adjacent nanowires is the main reason for the efficient absorption of metal nanowire arrays.On the basis of this,we proposed two dimensional metallic nanowires with four rotational symmetry of the metamaterial structure.The structure realize the polarization insensitivity of input wave,and broadband absorption in ultraviolet and visible regime.Meanwhile,we studied the influence of the shape change of nanowires on the absorption spectrum.