The Research On Structure And Performance Of Nematic Liquid Crystal Terahertz Modulators

Terahertz ?THz? region is between microwave and far-infrared. This specialregion have both advantages of optics and electronics. Terahertz wave has apromising application prospects in radar, communication and detection areas. Butterahertz devices are not available for application. The lack of high-depth andlow-loss modulators inhibit the development of THz communication and detectionsystems.The development of THz modulators is limited by the lack of THz functionalmaterials. Moreover, the interaction between THz wave and devices are notresearched completely. This paper researches liquid crystals performance in THzregion, and the interaction between THz waves. Based on nematic liquid crystals,THz modulators are designed and optimized theoretically and numerically. And theperformance of THz modulators are researched.Using order parameters describes the liquid crystal molecules orientation. Theinfluence by the electric fields is analyzed using elasticity theory. Solving thedynamic equation numerically, then get the liquid crystal molecules orientation. Theliquid crystal molecules orientation influences the transition of THz analyzed byJones matrix theory. Simulate the performance of the electric fields modulating theTHz waves.The PEDOT/PSS film is made on high-resistivity silicon in different thicknessusing spin coating. Measure the transmittance of the PEDOT film, and the influenceof the THz waves. Some sorts of sub-wavelength metal grating are designed, and thespectrum, polarization dependence and the potential distribution are calculatednumerically. One-dimensional metal gratings are made using lift-off. Thetransmittance of the gratings are measured. Two-dimensional metal periodicstructures are frequency selective surfaces. It has strong attenuation peaks at somecertain frequencies. And has good performance near the attenuation peaks. And themodulation performance causing by the dielectric refractive index altering arecalculated numerically.Polarizer-LCs-polarizer style THz modulators are made. The modulationperformance is researched experimentally. High modulation is reached. The LCsTHz modulators has a promising application in the THz imaging and detectingsystems..