The Problems of Measuring Dielectric Characteristics of Nano- аnd Microdimensional Mediums in Terahertz Frequency Range 100-3000 Ghz

The known quasi-optical methods of the phase and frequency measurements based on the application of Fabry-Perot wavemeters or traveling-wave wavemeters with mechanical micrometers have insufficient high-speed operation and preciseness. Using the quasi-optical units with piezoelectric control for measuring the spectral dielectric characteristics, it is possible to receive greater sensitivity of displacement when compared with the mechanical micrometers. Due to this fact, it is possible to solve the problems of measuring the amplitude-versus-frequency and amplitude-versus-phase characteristics of absorption in weak-absorbing materials (including thin dielectric films) by using a piezoelectric control of quasi-optical devices. The accuracy of phase shift measurements essentially increases the measurement sensitivity when using Michelson interferometer. However, for the thin films, the reflected signals in Michelson method may be superimposed on the main signal and they need to be taken into account. This requires a high sensitivity of phase division of the signals. One of the simplest methods is the one that uses a phase shift meter on quasi-optical units with piezoelectric control. At present, the work on modification of a number of classic methods and devices (generators and quasi-optical units) is carried out. The purpose of this work is to measure by using of these methods the most important characteristics of mediums over terahertz range (such as absorption factor and a refraction factor n). The best method for terahertz waveband is the method of dispersion Fourier spectroscopy. This method allows one to determine simultaneously the values and n with a high precision that is characterized by six significant digits for a refraction factor and is about 1% for the absorption factor.

To broaden the frequency range and increase the measurement preciseness of medium dielectric characteristics by the method of dispersion Fourier spectroscopy over terahertz frequencies from 0.1 to 3 THz, Central Institute of Measuring Equipment (CIME), Saratov, has developed and manufactured quasi-optical units with piezoelectric control and nanometric tuning. The proposed quasi-optical units have sufficient lateral section for a work on high power levels in terahertz band. Now, Central Institute of Measuring Equipment is carrying out an experimental-design work aimed at the creation of measurement complex for parameter control of a number of powerful pulse magnetrons (6 kW) over the range from 110 to 250 GHz intended for creation of high-power radio station.