Polarised interferometric spectrometry for the millimeter and submillimeter spectrum.

A method of interferometric spectrometry based on polarising beam-splitters is described. This allows operation over a wide range of spectral frequency without strong variations in efficiency, and also the suppression of the mean-level of the interferogram, spurious modulation of which is a major source of error in conventional methods. Interferograms obtained with this kind of spectrometer, in the far infra-red, are presented.