Methods for fast and accurate material properties estimate with terahertz time-domain spectroscopy in transmission and reflection with optically thick materials

With the development of terahertz time-domain spectroscopy, methods have been proposed to precisely estimate the thickness, refractive index, and attenuation coefficient of a sample. In this article, we propose a new method to compute these parameters. In this method, the attenuation is expressed in function of the refractive index. The theoretical unwrapped angle, which therefore only depends on the refractive index, is then matched to the experimental value. By applying already existing methods for estimating the thickness of an optically thick sample, the dielectric properties of the sample can be deduced. The method is applied both to the transmission and reflection spectroscopy. A demonstration of the method and a comparison with the previous methods are finally shown.