Patent ID: 8705032

Claim:
An ellipsometer or polarimeter system sequentially comprising: a backward wave oscillator (BWO); optionally a focusing lens; a rotatable image rotation system; a rotatable wire grid polarizer; a sample supporting stage; a rotating analyzer; a Golay cell; said ellipsometer or polarimeter system further comprising: an optical chopper; between said backward wave oscillator and said Golay cell; such that in use a polarized beam of Terahertz spectral range electromagnetic radiation is provided by said backward wave oscillator, is optionally focused by the focusing lens, has its polarization state rotated by said rotatable image rotation system and passes through said rotatable wire grid polarizer, then impinges on a sample placed on said sample supporting stage, reflects therefrom and passes through said rotating analyzer and enters said Golay cell; said ellipsometer or polarimeter system being distinguished in that, during data acquisition, the rotatable image rotation system and rotatable wire grid polarizer are functionally stepwise rotated in tandem, wherein said rotatable wire grid polarizer is stepwise rotated through a sequence of angles twice that of the rotatable image rotation system, such that the polarization state of the beam provided to the wire grid polarizer by the rotatable image rotation system, is passed by said rotatable wire grid polarizer even where the polarization state of the polarized beam of Terahertz spectral range electromagnetic radiation from the backward wave oscillator is rotated by 90 degrees.