Research On Metamaterials Based On Electromagnetically Induced Transparency

Recently, analogues of electromagnetically induced transparency(EIT) effects in metamaterials have received increasingly attention in electromagnetic fields. The EIT effect is one of hot issues in research areas of metamaterials. However, there are still many problems to be solved because the metamaterial with EIT effect(i.e. EIT metamaterial) is an emerging science. Constrast with other metamaterials, EIT metamaterial owns the more special work mechanism, and thus the optimizing of electromagnetic performance for EIT metamaterial has important theoretical research value and practical guiding significance. Therefore, in this paper, the electromagnetic mechanisms of microwave EIT metamaterials are taken as our breakthrough points. Using the mechanical oscillator model and the equivalent circuit theory, the generated mechnisms and key influence factors of EIT effects in metamaterials are analyzed. The construction methods of EIT metamaterials are investigated, and the performance tests and experimental verifications of EIT metamaterials in applications of microwave devices are accomplished.Firstly, the excitation mechinism of EIT effect in metamaterial is investigated. The analytical models of absorption power for EIT metamaterial are established from different angles. The generation reasons and influence factors of EIT effects in metamaterials are deeply analyzed. The working mechanism and excitation mechanism of EIT metamaterial are also explored. Moreover, Matlab simulation tool is used to analyze and verify the effectiveness of above analytical models.Secondly, the construction method of microwave EIT metamaterial is investigated. Based on the electromagnetic excitation mechanism of EIT metamaterial, three construction methods for EIT metamaterials with excellently electromagnetic properties are proposed, i.e. multi-band EIT metamaterial, tunable EIT metamaterial and EIT metamaterial based on microstrip line couplings. The effectivenesses of construction methods for EIT metamaterials are verified by numerical simulations and experimental measurements.Thirdly, this thesis designs a microwave polarization converter based on EIT metamaterial by using the high transmittance and strong dispersion property of EIT effect. For x- and y-polarization incident waves, the transmission coefficients of the designed metamaterial are same at 9.2GHz(~0.72), and their phase difference is 90-degree. Therefore, the highly transparent linear-to-circular polarization conversion can be achieved by using the EIT metamaterial. In addition, the thickness of polarization device is ultra-thin(~0.017l), and its thickness decreases two thirds than that of the reported polarization device. The effectiveness of the polarization converter is verified by numerical simulations and experimental measurements.Finally, this thesis investigates the narrow-band variable polarization properties of EIT metamaterial based on strong dispersion property of EIT effect. The designed metamaterial can achieve the linear-to-circular, linear-to-ellipse, and linear-to-linear polarization conversions in an extremely narrow frequency interval by altering the operating frequency. The narrow-band variable polarization properties of EIT metamaterial are demonstrated by numerical simulations and experimental measurements.From the above several aspects, by exploring the electromagnetic excitation mechanisms of EIT metamaterials, this thesis summarizes the construction rules and realization methods of microwave EIT metamaterials, and accomplishes experimental verifications of EIT metamaterials in applications of microwave devices, which have important guiding significance for the realizations of the microwave devices in the future. The research achievements of this thesis will not only help people to deeply understand the electromagnetic excitation mechanisms of EIT metamaterials, but also promote the rapid developments of EIT metamaterials in practical applications, which have important scientific significances and practical values for promoting the deeper developments of EIT metamaterials.