| In recent years,the field of terahertz-related technology has developed vigorously.As a new type of artificial composite material,metamaterials have unique properties that ordinary materials do not have.The desired magnetic permeability and permittivity can be obtained through specific design of the structure to achieve the purpose of manipulating electromagnetic waves.Metamaterials have a strong interaction with terahertz waves,so they are widely used in the field of terahertz technology.We have witnessed the rapid development of terahertz metamaterial resonance devices.As two typical resonance phenomena,Fano resonance and electromagnetically induced transparency have many unique characteristics,such as high Q values,asymmetrical line shapes,nonlinearity and slow light effects.They have potential applications in the fields of sensing,optical switch,communication,optical signal processing and optical pulse storage.The electromagnetically induced transparency and Fano resonance in the terahertz band based on metamaterials have attracted the attention of researchers.So far,various types of metamaterial resonance devices have emerged in endlessly,but most of the proposed designs have more or less problems such as poor tunability,single function and complex structure,which greatly limit the application of metamaterials resonators in the field of terahertz.In order to solve the scientific problems encountered above,this paper proposes several new types of terahertz metamaterial resonators based on the two resonance effects of electromagnetically induced transparency and Fano resonance.The specific research contents are as follows:(1)Design and research of tunable Fano resonance terahertz metamaterial resonator.A simple "H"-shaped metamaterial resonator is proposed.The slight break in the symmetry of the structure can realize the Fano resonance effect with a Q value of 43.The study found that the change of asymmetry can tune the Fano resonance,but the Fano resonance will disappear if it exceeds a certain range,and a broadband transparent window will appear.In addition,the size of the unit structure and the polarization angle of the incident electromagnetic wave also have a certain effect on the resonance response of the resonator.Finally,the general sample preparation steps and test methods of metamaterial resonators are briefly introduced.This tunable Fano resonance terahertz metamaterial resonator with high Q value can be widely used in sensing,filtering and other fields,and it can also provide a new idea for other researchers to realize Fano resonance.(2)Design and research of tunable dou-Fano resonance terahertz metamaterial resonator.A kind of S-type dual-Fano metamaterial resonator with tunable resonant performance is designed,which can realize the dual-Fano resonance effect with Q values of41 and 86 in the frequency range of 0.1-2.5 THz.The study found that the resonance frequency,transmittance and Q value of these two Fano resonances are all tuned by the structure asymmetry,and these two Fano resonances exhibit completely different states under different structure asymmetry.The refractive index sensors made for the two Fano resonance dips have FOM values of 12.9 and 16.5 respectively,which basically meet the working requirements of the sensor.In addition,by introducing photosensitive silicon in a specific area of the resonator structure,the use of an external light field to adjust the conductivity of silicon can basically realize the function of a terahertz optical switch.(3)Design and research of dual-function terahertz metamaterial resonator with electromagnetically induced transparency and Fano resonance.A meta-material resonator composed of a square ring resonator and an embedded split ring resonator is proposed,which can simultaneously achieve Fano resonance with a Q value of up to 123 and electromagnetically induced transparency with transmittance of 85.9%.With the aid of the coupling theory,the mechanism of the two resonances is analyzed,and the cause of resonance is further explained through the electric field distribution at the resonance frequency,so as to ensure the reliability of the conclusion.The study found that the transparent window and the Fano resonance dip are tuned by several structure parameters,and its transmittance and resonance frequency change with the change of the structure parameters.The terahertz metamaterial dual-function resonator has broad application prospects in fields such as terahertz sensing and filtering.(4)Design and research of broadband adjustable electromagnetic-induced transparent terahertz metamaterial resonator.A metamaterial resonator composed of three metal bars is designed.The resonator can obtain a wide-band transparent window with a bandwidth of up to 1.212 THz by means of multi-mode coupling and superposition.Since the transparent window generated by the resonance is not caused by the electromagnetically induced transparency effect achieved by the traditional light-dark mode coupling or the bright-light mode coupling,the resonance is called electromagnetic-induced transparency to distinguish it.Further research found that the change of the structure parameters can realize the regulation of the resonance frequency of the resonance dip and the bandwidth of the transparent window.Finally,the application prospects of the resonator in the field of terahertz optical switches and communications are briefly prospected. |
