Research On Broadband Terahertz Absorber Based On Metamaterials

Metamaterials,as a new type of artificial materials,can obtain arbitrary electromagnetic parameters by changing their periodic structure parameters and geometric shapes.It overcomes the disadvantage of bulky natural material,improves the flexibility in frequency selective absorption,and is the first choice material for people to design frequency selective absorber.Traditional metamaterial wideband absorbers generally use the combined action of multiple narrowband absorbing metal resonators with similar frequency to achieve the wideband absorption effect.This method has two main disadvantages:First of all,once the geometric shape and structural parameters of the metamaterial are fixed,its absorption performance is basically fixed,and it lacks certain dynamic tunable ability and flexibility.Secondly,good performance of the broadband absorber often need to design more complex geometric shape of the top metal,or need to design a multi-layer structure or use a fractal resonator,etc.,is not easy to practical application of processing and manufacturing.In this paper,two new metamaterial broadband absorbers are proposed to overcome the two shortcomings of traditional broadband absorbers.1.A terahertz wide band absorber with tunable absorption intensity and bandwidth based on vanadium dioxide material is designed.The absorption intensity and bandwidth of the incident wave are dynamically tunable in the frequency range of 1.436-3.448 THz by using the sensitivity of the metallic and non-metallic states of vanadium dioxide to temperature.The full-wave simulation shows that the absorption rate is more than 90%in the operating frequency band when the vanadium dioxide is a metal state.By changing the temperature value,with the increase of the conductivity of vanadium dioxide,the absorption formants are significantly enhanced and the number of absorption peaks is significantly increased.The absorption intensity increases from only 7%to more than 90%at the center frequency of 2.442 THz.The absorber is insensitive to polarization angle and performs well over a wide range of incident angles.2.An ultra-wideband terahertz absorber based on doped silicon material is designed.Its structure consists of square silicon ring and silicon substrate,which overcomes the shortcomings of traditional metamaterial broadband absorbers that need to design complex metal patterns and multilayer structures.The full-wave simulation shows that the designed absorber has four absorption peaks in the range of 0.7 to 5.7 THz,and the peak absorption rate is more than 97%.The unique structure of the absorber makes the absorption independent of the polarization angle,and the absorption performance remains constant at small incident angles,and it still exhibits good performance in a wide range of incident angles.