The Study On The Regulatory Mechanism And Theoretical Characteristics Of Topological Electromagnetic Structures

In the past ten years,the development of topological band theory has provided a split-new and effective method to manipulate the propagation of electromagnetic wave.A series of topological photonic phenomena,including topological protected edge states,the selective excitation of bulk states,photonic Weyl points and so on,are observed by utilizing artificial crystals,such as photonic crystals and designer surface plasmon crystals(DSP crystals).And these fascinating phenomena are great significance to the advancement of communication,photonic devices and quantum computing and other fields.However,for this type of artificial crystal structure,its electromagnetic response characteristics have been defined in the process of design and processing,thus limiting its potential application to a certain extent.Based on this,in this dissertation,by introducing nematic liquid crystal as the constitute material of the designed topological artificial crystals,the tunability of related topological phenomena are realized under the driving of external action.The details of this dissertation are listed as follows:1)A DSP crystal consisting of two metallic layers is proposed to realize topological valley states which was demonstrated by numerical simulation.And the evident chiral locked bulk valley-selective excitation was observed for the first time in this type structure.Moreover,the switchable excitation of bulk states and broadband valley-projected edge states were realized with the help of nematic liquid crystal.A switchable energy coupler was designed by combining the switchable bulk states excitation with the valley-projected edge states,and the coupling efficiency exceeds 75%.2)A terahertz one-dimensional photonic crystal consisting of liquid crystal and PDMS is proposed to realize generalized Weyl point in synthetic space which was verified with numerical simulation and theoretical calculation.The phase vortex of reflection near the generalized Weir point in the parameter space are also observed ensuring the existence of interface states.Using the variable refractive index of liquid crystal under the action of magnetic field,the frequency of the generalized Weir point can be adjusted.