In a polarizing Fourier’ spectrometer the spectral information is contained in the interference pattern of polarization states as the function of the path difference. This is especially useful at low frequencies, where polarizing beamsplitters are much more efficient than non-polarizing ones.
In Faraday configuration light propagates along the magnetic field while the propagation of light is perpendicular to the magnetic field in Voigt configuration.
The TeslaFIR spectrometer is an automated instrument which enables the measurement of spectra in the energy range from 200cm-1 down to 2cm-1. It uses a mercury arc lamp as the light source in a polarizing (Martin-Puplett) interferometer SPS-200, and detects light with a bolometer that is cooled to 0.3K by pumping on He3. The samples can be cooled down to 2.5K. The cryostat is equipped with a 17T magnet, where samples can be mounted in Faraday and Voigt configurations for measuring absorption spectra. There is a separate insert for reflection measurements.
The interferomerometer can be copuled with a dilution refrigerator, where absorption spectra can be measured of samples at 100mK in magnetic fields up to 12T.