Abstract
Terahertz Spectroscopy is characterized by the electromagnetic radiation with frequencies in the range from 0.1 to 20 THz (~ 3.3 to 667 cm-1). Due to instrumental limitations, this spectral region was known as the "terahertz gap", and for many years it remained unexplored. The low and high frequency borderlines were limited by electronic and optical devices of generation of radiation, res…