Material parameter extraction for terahertz time-domain spectroscopy using fixed-point iteration

A simple method to extract the far-infrared dielectric parameters of a homogeneous material from terahertz signals is explored in this paper. Provided with a reference, sample-probing terahertz signal and a known sample thickness, the method can determine the underlying complex refractive index of the sample within a few iterations based on the technique of fixed-point iteration. The iterative process is guaranteed to converge and gives the correct parameters when the material thickness exceeds 200 μm at a frequency of 0.1 THz or 20 μm at a frequency of 1.0 THz.