Cavity methods of investigation of gas and condensed medium in MM AND SubMM ranges

For MM and SubMM ranges, on the basis of high-quality Fabry-Perot resonator the original precision methods of investigation are discussed: atmospheric absorption, including continuum absorption; radiant reflectance of metals; refraction index and loss tangent of dielectrics, including films and liquids. The methods of measurement are absolute ones and self "calibrated" that means it is not necessary to use the prior information. Concrete values are calculated on the basis of measuring of adjustment frequency and line width of empty and loaded resonator. The temperature range is 80 K-900 K for investigation of condensed medium; for atmospheric — from −30 C up to +60 C and at humidity — 0%–80%. The measurement results of latest polymeric materials are presented.