A method of studying spectral optical characteristics of a homogeneous medium by means of terahertz time-domain spectroscopy

Abstract

We have developed an algorithm for solving an inverse problem related to the reconstruction of spectral dependences of terahertz (THz) optical characteristics of a homogeneous medium in the form of a plane-parallel plate, which is based on processing signals obtained by a THz time-domain spectrometer. In contrast to existing methods, the developed algorithm allows studying the optical properties of dielectric samples that have a small thickness (down to 0.1 mm) and low index of refraction. Optical characteristics in the THz spectral range are determined by minimization of the error functional constructed based on experimental and theoretical complex transfer functions of the sample, wherein the theoretical transfer function is obtained by using a model of a Fabry-Perot quasi-resonator. The proposed method is experimentally verified by studying optical properties of test samples. The reconstructed THz optical characteristics are compared with the characteristics of the same test media obtained by means of the THz backward-wave oscillator spectroscopy, which allowed estimating the accuracy of the proposed method.