| Terahertz(THz)wave is a kind of electromagnetic wave with a frequency in the range of 0.1 to 10 THz.At present,the application of THz wave is far inferior to its adjacent band,forming a so-called "THz gap".However,the emergence of metamaterials has overcome the limitations of materials’ natural properties and created the basic conditions for the development of THz technology.It has been confirmed that the interaction of metamaterials and electromagnetic radiation can realize the control of THz wave.On this basis,through the study of the split ring metamaterial and the wire-grid structure,the multi-frequency high-Q Fano resonances are realized,and the THz wire-grid reflector and Fano resonance switch are proposed.The details are as follows:1.Based on studying the mechanism of Fano resonance,two new asymmetric split ring structures were designed.One is the variant of the split ring.When y-polarized THz wave is normally incident,the dual-frequency high-Q Fano resonance(F1,F2)and dipole resonance are generated in the spectrum.The other is the split ring nested structure.Compared to the variant of the split ring,the new high-Q Fano response(F3)is triggered at 0.891 THz.In theory,the resonance intensity and Q value of each Fano resonance can be tuned by adjusting the structural parameters,and the Q values of F1,F2,and F3 can reach up to 43.9,78,and 69.3,respectively.2.Based on the indium tin oxide wire-grid structure,the terahertz reflector with optical transparency and adjustable reflectivity is proposed.The reflector has a tunable THz reflectance from 0.5 to 0.97 in the THz frequency range(0.22–0.5 THz)and a high optical transmittance of approximately 60% in the wavelength range of 450–800 nm.The light irradiation path in the terahertz system is optimized by this transparent reflector,and the overall performance of the system is improved.3.Based on the theoretical study of the composite structure of wire-grid and split ring variant,a new Fano resonant switching device is proposed.Due to the sensitive characteristics of Fano resonance,the response amplitude of the device is controlled by the variable conductivity of the active material.And the resonance characteristics of the ring structure are weakly affected by the wire-grid electrode.This composite structure design provides a new idea for the control of THz wave. |
