Electromagnetic Properties Of Tunable Terahertz Metamaterials

The Metamaterial is a kind of artificially designed periodic sub wavelength composite structure.By setting its geometric parameters,the electromagnetic characteristics of electromagnetic wave can be adjusted,which is of great significance in the future communication,medical and security fields.However,when the metamaterial structure is fixed,its performance is limited and it is difficult to achieve dynamic tuning.Perovskite and molybdenum disulfide have excellent photoelectric properties,which can be combined with metamaterials to achieve the purpose of dynamic tuning.In this paper,terahertz metamaterials based on perovskite and molybdenum disulfide thin films will be prepared.The electrical conductivity of the active materials will be regulated by external light excitation to realize the dynamic tuning of the electromagnetic properties of the metamaterials.The main research contents are as follows:1.In this paper,a metamaterial structure based on fully symmetrical metal split ring structure unit is proposed.The transmission characteristics of incident waves in different polarization electric fields are simulated by software,and the surface electric field strength and surface current of the metal unit structure are analyzed to reveal its electromagnetic response mechanism.On this basis,metal metamaterials were fabricated by lift off photolithography.The microstructure and thickness of deposited metal were observed by optical microscope and SEM,respectively.The samples were tested by terahertz optical pumping time domain test system.Due to the symmetry of the structure,the resonance effect of TE wave and TM wave penetrating the metamaterial sample is almost the same,which indicates that the structure is not sensitive to the polarization direction of the electric field of the incident wave2.Perovskite Thin Films with organic-inorganic cross structure were prepared by spin coating process.The structure and optical properties of Perovskite Thin films were characterized.It is found that the perovskite films prepared by spin coating process have full grains,dense growth,no impurity phase and good optical properties.On this basis,perovskite thin films were further spin coated on the metamaterials,and the terahertz time-domain system test was carried out on the experimental samples.With the increase of pump power,the terahertz resonance amplitude gradually weakened.The results show that the dynamic tuning effect of perovskite is achieved by external light excitation,and the tuning depth is 20%3.The selection of precursor solvent and stabilizer of molybdenum disulfide was compared and analyzed.The corresponding molybdenum disulfide film was prepared and its optical structure was characterized.On this basis,the terahertz metamaterials based on Mo S2 were prepared,and the terahertz time domain system was tested.Under different external light excitation,the dynamic modulation effect is achieved,but the resonance amplitude does not change significantly,and the modulation depth is low.The reason may be that the concentration of molybdenum disulfide powder is too high,resulting in agglomeration effect,resulting in poor film quality.In addition,the higher resistivity of intrinsic silicon substrate also affects the modulation depth.