Design And Research Of Modulator And Filter Used In THz Wave Band

It is difficult to select the materials in the designs of the THz devices, because most of the materials would lead to high loss, high absorption and high dispersion in the transmission of the THz wave. The metamaterials can realize the integration and miniaturization of the THz systems bringing new hope to the researches of the THz devices. Based on the metamaterials, we have finished three aims: the design of a bi-directional tunable terahertz modulator; the design of single band-stop and dual band-stop terahertz filters; the design of single band-pass and dual band-pass terahertz filters.An asymmetric structure which is based on the semiconductor silicon substrate has been chosen as the basic unit to realize two resonance frequency points of 0.35 THz and 0.73 THz by periodic extension in the design of the bi-directional tunable terahertz modulator. The bi-directional tunability of frequency(simultaneously red-shift and blue-shift) can be achieved by changing the conductivity of the silicon under different gaps of the substrate. The new resonant frequency points are 0.61 THz and 0.42 THz. According to the electric field distributions of resonant frequency points, the change trends of resonant frequency points and bandwidth under different structure parameters are analyzed. The stability of transmission for different terahertz wave incident angles and polarization directions are also studied. There is a very minimal impact on the resonance frequency when θ changes from 0°to 45° A new resonance frequency point of 0.77 THz could been realized when ? changes from 0°to 90°. Besides,the influence of light transmission depth on the transmission coefficient is researched. The model has been fabricated and the simulation result is basically consistent with the test result. Then, the design of a split ring resonator the resonance frequency point of witch is 0.46 THz is completed. The comparison between the results of simulation and test is given and they are in good agreement.We adopt an organic material as the substrate and the deformation of a split ring resonator as the basic unit. Single band-stop and dual band-stop terahertz filters have been designed using the two-layer structures. The bandwidths of the single band-stop filter are 0.16 THz and 0.47 THz under different polarization directions of the incident wave. The bandwidths of the dual band-stop filter are 0.09 THz and 0.1 THz and the slopes of the edges are 297 dB/THz,297 dB/THz,287 dB/THz,and 354 dB/THz. Through the distributions of the electric field and current, we analyze how the main parameters affect the characteristics of the stop-band such as bandwidth and the slope of the edges. Besides, the stability of transmission for different incident angles and polarization directions of terahertz wave is studied. The credibility of the results is verified by the principle of two-layer stack and the CST electromagnetic simulations. The split ring resonator above also indirectly proves the reliability of the filters.In the end, the corresponding single band-pass and dual band-pass filters using the complementary structures of the band-stop filters have been shown. The bandwidth of the single band-pass filter is 0.52 THz. The bandwidths of the dual band-pass filter are both 0.18 THz.