Based On The Fdtd Theory Of Subwavelength Metal Holes Array Terahertz Transmission Simulation

In this work, we used the results of FDTD simulation to investigate the enhanced transmission of the sub-wavelength metallic periodic holes arrays. The main work of this article as followed:We presented the enhanced transmission spectrum of a copper foil with the sub-wavelength fractal structures by means of the terahertz time domain spectroscopy (THz-TDS) and finite-difference-time-domain (FDTD) simulation. In the view of FDTD simulations, respectively, we studied the influence of the electric field and magnetic field on the enhanced transmission of THz wave through each level of fractal pattern generated by the repeated affine transformations of an H-shaped mother element on the copper foil. We simulated the incidence and transmission of THz wave, and showed the propagation and distribution of the interior electromagnetic field by the software of electromagnetic design named CONCERTO 6.0. To compare with the experimental results, we simulated the cases that the certain levels of the pattern are deleted. The results of simulation agree with the experimental one. It is found that the transmission enhancement in the low frequency regime is caused by the radiation of electron resonance in the low fractal levels, and the transmission enhancement in the high frequency regime is caused by the radiation of electron resonance in the high fractal level, that is, the localization resonance of fractal structures. These results indicate that the slits with fractal structure in the metallic foils act as a waveguide. The vertically incident THz wave is coupled with the surface plasma, which form into surface plasma polaritons, so that the enhanced transmission is generated.According to the simulation of THz transmission of rectangular holes with the same area and different ratio between the length and width, we investigate the distribution of the electric field along the direction of the length and width of rectangular holes. At the same time, THz transmission spectra of rectangular holes in the metallic foils are simulated. The simulation agrees with the experimental results.The simulation to THz transmission through some small holes in the metallic foils presents a powerful tool for the design and numerical analysis of THz optical devices. At the same time, the mechanism of the enhanced transmission of THz wave through the holes array on the metal is analyzed theoretically. The modulation ability of metallic mesh structures to the electromagnetic wave is going to provide a powerful tool for the design of THz photonic devices.