the waveguide passive spectrometer based on
the cooled selective detector
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.