The Design And Research Of THz Modulators, Filters Which Based On Metamaterial

Terahertz (THz, λ=30~300μm,1~10THz) radiation has broad applications inmany fields, THz sensing, imaging, spectroscopy, communication, and so on.However, due to the scarcity of THz functional devices used to control andmanipulate THz waves, the application technology in the THz ra nge is still far lessdeveloped than that in other frequency ranges. Metamaterials open the new path forthe manipulation of THz wave and novel THz devices. The strong resonance andtunability of metamaterials at THz frequencies makes them suitable for fabricatingTHz functional devices. In this dissertation, THz-wave functional devices(Modulators, filters) based on metamaterials has been designed and studied.The main research contents and innovation points can be summarized as follows:1. We present a reverse nested ring resonators (SRRs) within THz regime. Wecompare the transmission of three different cases (two rings nested, separate outerring and separate inner ring) and analyze the distribution of its electric fields and thesurface currents to make clear of the resonance characteristics and resonancemechanism. We also utilize an improved method to retrieve the effective parametersof our design by calculating the scattering (S) parameters.2. Single split-ring resonator, asymmetric planar dual-split-ring resonator andnested split-ring resonators are designed and their characters are simulated in the THzregion. Gallium arsenide is inserted between the gaps of split-ring resonators, throughmodulation of conductivity of gallium arsenide, we have ac hieved the switching ofdifferent resonance modes, and these designs can be used as THz modulators. In thethird quarter, we also researched the working mechanism of our designs by analyzingthe current and electric field distributions.3. We propose a double-layer opposite arranged three-dimensional invertedgrating plasmonic crystal, and its transmission and filtering properties have beeninvestigated in the terahertz regime. Simulation results show that our design hasexcellent filtering properties. It has wide bandgap and passband with steep band-edgesand the transmittance of passband and forbidden band is almost close to1and0,respectively. As the distance between two plates increases, the resonance frequency exhibits a gradual blueshift from0.51THz to0.81THz. Therefore, we candynamically control the bandwidths of bandgap and passband by adding apiezoelectric ceramic between the two plates. Furthermore, the dispersion relations ofmodes and electric field distributions are presented to analyze generation mechanismsof bandgaps as well as offer a reasonable explanation for the location of bandgaps aswell as the frequency shift phenomenon.