Overview of Data Analysis Techniques of Frequency-Domain Terahertz Spectroscopy

Chemical analysis is widely used in different fields. It is based on spectroscopy and different methods. One of the upcoming technology is terahertz (THz) spectroscopy, but it is not yet well researched. This paper presents opto-electrical methods for generating THz waves and it presents frequency-domain spectroscopy as the possible solution to problems, that are presented in infrared, visible-light, ultraviolet, x-ray and gamma spectroscopies. Basic analysis techniques are presented, including deriving absorption coefficient and refractive index. Both are interconnected with Kramer-Kronig relation and are fundamental sample characteristics that can be measured with spectrometers. Example of measuring transmittance and refractive index are presented in experiment, made with frequency-domain spectroscopy platform TeraScan 1550.