Efficient optimization approach for accurate parameter extraction with terahertz time-domain spectroscopy

We propose a novel optimization algorithm for the extraction of material complex refractive index in the terahertz (THz) frequency range. The algorithm is applied for materials with arbitrary frequency dependence. We utilize dispersive dielectric models for accurate parameter extraction of a sample of unknown thickness. This approach allows for simultaneously estimating the parameters and fitting them to one of the dispersive models of the materials in the THz frequency range. Our approach has been successfully illustrated through a number of examples with different dispersive models. The examples include the characterization of doped semiconductors used in surface plasmon plaritons in the THz regime. They also include characterizing carbon nanotubes.