New Opportunities in Quasi-Optical Materials Characterization in Far Infrared Region

Fourier-transform infrared (FTIR) and Time-Domain (TDS) spectroscopies are widely used for material characterization of materials in far infrared region. The main disadvantage of them is limited measurement dynamics especially in lower frequency range. They also require using very thin samples in case of lossy materials. New generation of vector network analyzers (VNA), which are very well known in microwave band, allow measurements in frequency domain up to 1.5 THz with very high dynamics above 90 dB. Moreover, the amplitude and the phase of signals can be measured at 32001 frequency points with 1 Hz resolution. These advantages create new opportunities in frequency domain characterization of different types of materials, both lossless and lossy. In this paper a new broadband measurement technique suitable for far infrared range is presented. What is interesting this method does not require any information about thickness of samples under test. Therefore, the electromagnetic properties of different materials (e.g. gases, solid and liquid materials) can be obtained.