| Metamaterial absorbers have become an important research hotspot in the field of metamaterials due to their important application value in stealth,detection and communication.With the depth study of metamaterial absorbers,it is found that the single-frequency absorbers are no longer sufficient to meet actual needs.Therefore,it is very important to design and manufacture a metamaterial absorber with amplitude modulation characteristics.Based on the conductivity of graphene under the action of electric field and light field,a single-frequency amplitude adjustable metamaterial absorber with a mixture of graphene and metal was designed and simulated by CST Microwave Studio software.The results showed that changing the Fermi level of graphene can achieve the modulation of the center frequency amplitude and the modulation depth can reach up to 58.6%.When the graphene Fermi level was 0eV,the change of structural parameters can cause a regular shift in the center frequency of the absorber.The metamaterial absorber with adjustable wide frequency amplitude was designed based on the single-frequency metamaterial absorber and the principle of superimposing the extended bandwidth of different size structures.The graphene Fermi level and the influence of incident angle of metamaterial were simulated and analyzed.The results showed that the average absorption rate was 96% when the broadband absorption band was 15.8~18.9GHz at 0eV,and the absorption rate was reduced to 57% at 0.3eV.The modulation depth was 40.6%,and the absorption effect for all incident angles was approximately the same.Through the analysis of the performance of graphene and metal materials,two lithography and etching processes were used to complete the fabrication of metamaterials of metal cross and graphene square ring.The spatial wave method was used to test the absorption rate of broadband metamaterial absorbers under different applied voltages.The results showed that the average absorption rate was about 70% and the bandwidth was about 2.8GHz when the applied voltage was 0V.And when the applied voltage was 22 V,the average absorption rate dropped to about 48% and the electronically controlled modulation depth was 31.4%.The test found that the addition of externally applied optical pump energy can increase the modulation depth of the metamaterial absorber.The electro-optic modulation depth was increased to 42% when the applied voltage was also 0V and 22 V and the pump energy was 17 mW.The absorption curve of the broadband super material absorber at different applied voltages was tested by using the spatial wave method.The test results showed that when the applied voltage was 0V,the average absorption rate was 70%,the bandwidth was about 2.8GHz.And when the applied voltage was 22 V,the absorption rate drops to 48%.The electronically controlled modulation depth was 31.4%,which is consistent with the trend of simulation results.In order to increase the modulation depth of the metamaterial absorber,an external optical pump was introduced at the same time as the bias voltage was applied,and the absorption rate was tested.The test results showed that the electro-optic modulation depth can be increased to 42%.The results showed that the metamaterial adjust the electronically controlled amplitude and superabsorbent based on the adjustable conductivity of graphene.Broadband absorption can be achieved by superimposing different sizes of graphene-metal hybrid structure absorbers.The amplitude of the broadband absorber can be adjusted by changing the carrier voltage of the graphene to change the carrier concentration of the graphene.And adding externally applied optical pumping energy while adding a bias voltage can increase the modulation depth. |
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