Analysis of the waveguide passive spectrometer based on the cooled selective detector

 

 V. V. Zavyalov
P.L. Kapitza Institute for Physical Problems, RAS,
Moscow Institute of Physics and Technology (MIPT)
 

The paper is received on January 3, 2015

 

Abstract. The procedure of measurements and the formulas for calculating the sample's reflection (R) and transmission (T) coefficients  with the use of  a passive terahertz spectrometer are presented. The passive spectrometer comprises of cold and room-temperature chambers interconnected via a multimode waveguide (light pipe).  Spectral selective liquid helium-cooled   detector is placed at the cold side,  and  a specular disk shutter is positioned near the  room-temperature end of the  light pipe. The metered coefficients R and T can be calculated as a result of the two consecutive synchronous detection measurements — with the specimen placed before and after the shutter. Passive terahertz spectrometry based on the selective cooled detectors is a good alternative to active one when the use of a sophisticated teraherz radiation source is difficult or undesirable.

Key words: Terahertz spectroscopy, passive spectroscopy, radiometry, thermal radiation, light-pipe.