Research Of High-performance Dielectric Absorbers Based On Metamaterials

As a kind of synthetic materials composed of periodic arrangement of sub-wavelength unit structures,metamaterials have some special electromagnetic characteristics that many natural materials cannot achieve.At the same time,the metamaterial absorbers have been developed rapidly since they were proposed,and people's requirements for their performance and applications are constantly improving.Because absorbers with metal structures often have shortcomings such as narrow absorption band,high complexity,and difficulty in tuning,more and more non-metallic materials with excellent performance have been gradually used in the design and manufacture of metamaterial absorbing structures in recent years.In this article,the design and simulation of non-metallic high-performance metamaterial absorbing structures are carried out in the microwave and terahertz frequency bands respectively.The main contents are as follows:(1)Based on the unique electromagnetic characteristics of water in the microwave frequency band,an annular water-based metamaterial absorbing structure with ultra-wide absorption band is proposed.The simulation results show that the structure can always maintain an absorptivity of more than 90% for the incident wave in the8.20-78.32 GHz frequency band,and the absorptivity at resonance points are close to100%.Compared with many absorbing structures of the same type,the absorption bandwidth of the structure has been greatly improved.In addition,by studying absorbing characteristics of the structure under a variety of different conditions,the results show that the water-based absorbing structure also has excellent properties of polarization independence,wide-angle incidence,and thermal stability.At the same time,the structure can be prepared by 3D printing technology,which not only greatly reduces the complexity and production cost,but also better meets the optical transparency and flexibility of the material.The water-based metamaterial absorber can be used in the fields of electromagnetic stealth,microwave anechoic chamber,and prevention of electromagnetic radiation and leakage,which provides ideas for the design and application of broadband absorbing structures in the microwave band.(2)A graphene-based tunable metamaterial absorbing structure that works in the terahertz frequency band is proposed,and the working performance of the structure can be tuned by applying external voltages.The simulation results show that when the voltage value is 0.6e V,the absorptivity of the absorber at 4.59 THz can reach 99.98%,and when the voltage changes within 0.4-0.8e V,the tunable range of the operating frequency is 3.88-5.11 THz.When the graphene units are divided into two groups according to a certain rule and different voltages are applied respectively,two sets of absorption peaks with high absorptivity and independently adjustable appear.By controlling the voltage value,not only can one set of resonant frequencies be adjusted separately,but also the independent tuning of the two absorption peaks can be achieved.And when the two sets of voltages change in the range of 0.5-0.7e V and 0.8-1.2e V,the tunable frequency ranges are 5.43-6.28 THz THz and 7.08-8.48 THz respectively.In addition,the simulation results show that the absorbing structure also has the characteristic of being insensitive to the angle of the incident wave,and can produce electromagnetic response to subtle changes in the refractive index and thickness of the sample under tested.All of the above prove that compared with traditional terahertz metamaterial absorbers,the graphene tunable absorbing structure not only has higher flexibility,but also has important application value in the fields of terahertz sensing and tunable electromagnetic devices.