Validation of thick materials having high refractive indices as highresistance silicon plates with THz-TDS

In order to evaluate the optical constants of the materials having high refractive indices in THz region exactly, a THz-TDS instrumental set-up has been modified. As such a kind of samples, high-resistance silicon plates were used. The properties were estimated adequately when THz waves radiate in parallel flux, while those were improper with converged waves. The THz-TDS system was designed to easily exchange the parallel/converged configuration.