Surface and volumetric scattering by rough dielectric boundary at terahertz frequencies

Abstract

In the terahertz (THz) band, materials that could be seen as smooth and homogeneous at microwave frequencies may display surface and volumetric scattering behavior. In this paper, we apply the integral equation method (IEM) and the vector radiative transfer (VRT) theory to simulate surface and volumetric scattering by a rough material boundary, respectively, in order to study the scattering characteristics of targets at THz frequencies. IEM was used to calculate the backscattering coefficient of a metal plate, in which the calculated results have good agreements with measured data, proving the applicability and superiority of IEM to the metal materials. Nevertheless, the simulation results of dielectric sample using IEM cannot fit the measured data. That is to say, for dielectric boundary, we should not only consider the contribution of surface roughness, but also the contribution of internal microstructures. We propose to use both VRT and IEM to simulate the scattering behavior of dielectric targets, which shows good agreement between the simulation and measurement. The results tell us that for the material which presents metal features, we only need to consider the effect of surface roughness; however,for the dielectric material, the micron inclusions of the material also need to be considered, i.e., carbon powder and silicon carbide particles. The established model can also be used to simulate the bi-static scattering coefficient, which can be regarded as a complement to the experimental data.