Research On Electromagnetically-induced Transparency Based On Metamaterials In Terahertz Band

Metamaterials have attracted much attention in scientific research because of their unique properties, which are not available in most conventional media, and have many novel physical phenomena. The study of electromagnetically-induced transparency (EIT) based on metamaterials has also caused some research upsurge. Because the electromagnetically-induced transparency can change the dispersion property and slow down the speed of light, it have an important application in the slow-light devices, non-linear devices, filters, optical storage and sensors. The use of metamaterials can achieve the electromagnetically-induced transparency in the terahertz wave band which overcomes many problems and complex experimental conditions in the quantum system. In this paper, the electromagnetically-induced transparency based on metamaterials are studied in the terahertz-band,and several kinds of electromagnetically-induced transparency structures based on metamaterials are designed. Simulation are carried out by using the numerical simulation software CST. The study of these structural design methods, electromagnetic properties and coupling mechanism, to promote the practical application of the characteristics has a certain significance. The main work is as follows:(1)Two kinds of EIT structures based on the coupling of the bright mode and the dark mode are designed. One is a polarization-sensitive opposite-edge opening square ring structure and the other is an optimized polarization-insensitive adjacent-edge opening square ring structure. The CST simulation of the two structures in the TM polarization direction and TE polarization direction of the transmission spectrum were analyzed and the surface current distribution of the two structures was analyzed to explain the physical mechanism of electromagnetic response characteristics. At last, the tuning of the EIT phenomena of the adjacent-edge opening square ring structure is studied by changing the geometric parameters of the structural element.(2)Three kinds of EIT structures based on the coupling of the bright mode and the bright mode are designed, in which the single-ring structure is polarization sensitive, the cross-ring structure and the double-ring structure are polarization insensitive, and both EIT resonant peak transmittance are up to more than 90%. By analyzing the structure of the two substructures, the transmission spectra of the two substructures were studied and the causes of the EIT phenomena of these structures were analyzed with the transmission spectra of the original structures, and several main parameters were studied. The effect of structural parameters on the resonant frequency, linewidth and resonant intensity of three resonant points of EIT was analyzed. The tunability of metamaterials in terahertz band was realized.(3)Since the transparent windows of the EIT structure are usually at a fixed frequency, adjusting the frequency range or amplitude of the transparent window usually need to change the geometrical parameters of the structure, which is difficult to achieve for the machined structure.In this paper, by changing the applied voltage, the EIT can be dynamically tuned by introducing the graphene material which is hot compared with the current research, avoiding the trouble of changing the geometric parameters. By introducing the graphene material into the opposite side opening structure and the adjacent opening structure, it is analyzed by CST simulation that the graphene-based side opening structure can meet the requirement of polarization insensitivity by changing the incident angle of the incident wave. The adjacent-edge opening structure is a polarization-insensitive structure.The transmission spectra and surface current distributions of the two structures were analyzed. The generation principle of EIT was analyzed. The change of the geometrical parameters and the change of the angle of the incident electromagnetic wave are studied. Finally, the resonance frequency and the amplitude of the resonant peak of EIT are dynamically adjusted by changing the applied voltage to the structure.(4)Based on the above theoretical analysis and simulation, the design of several EIT structures were processed and tested. The terahertz time domain spectrum THz-TDS system was used. It is found that the test results of the designed structure are in good agreement with the simulation results, which provides technical support for the realization of the polarization-induced polarization-induced electromagnetic structure of the terahertz band.