Research On Terahertz Waves Electromagnetic Properties Of Carbon Nanotubes

THz has unique characteristics of penetration, low energy, broadband and spectral resolution. THz have wide range of applications, and will have far-reaching impact on the imaging technology, spectroscopy technology, communications technology and safety testing. Emergence of nano materials has brought new opportunities to the terahertz development. Nanotubes with attractive intrinsic properties, have been widely concerned. Applications of carbon nanotubes have also been extended for DC to infrared regions. However, little basic research of carbon nanotubes in the terahertz region compared to the microwave and infrared regions has been studied.The electromagnetic propagation characteristics of carbon nanotubes(CNTs) under normally incident is investigated at Terahertz(THz) frequencies. The effective Maxwell-Garnett model and Drude-Lorentzian model of CNTs(SWNTs, DWNTs, Hdoped CNTs) are used. In this paper, curves of carbon nanotubes permittivity, dielectric loss tangent and real conductivity varies with frequency are given. The field and current equations that describe waves in CNTs and metals are derived and discretized based on the Auxiliary Differential Equation Finite-Difference Time-Domain(ADE-FDTD) method. The validation of the method and program is performed. The shielding effects of carbon nanotubes with different thicknesses are compared numerically. FDTD numerical results demonstrate that CNTs have potential applications in Terahertz electromagnetic interference shielding. The influences of the silicon substrate on the propagation of Terahertz waves through a stratified media slab containing CNTs are discussed. Some phenomena, for example multiple reflection and transmission are observed.The chiral vector of Carbon nanotube determines its structure, and also determines many of its physical properties. By analyzing the chiral material, combined Condon model and Drude-Lorentz model, a chiral carbon nanotube model for FDTD calculations have been proposed. In this paper, field equations iterative formula with ADE-FDTD method to a chiral carbon nanotubes are derived, and the terahertz wave reflection coefficient and the transmission coefficient of the chiral carbon nanotubes are calculated. Analysis of chiral carbon nanotubes, the results show that the chiral carbon nanotubes in the presence of optical rotation and circular dichroism, which later application has a certain reference value. Finally, the chiral media is studied by the equivalent circuit, then the phase shift and the characteristic impedance per unit section of an equivalent circuit is given and verified by ADS.