Proceedings PaperPolarization and optical aperture synthesis: the problem and a solution
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For the interferometric environment, optical polarimetry may need to assimilate radio-polarimetric concepts. In particular, the Stokes parameters should be defined in terms of complex correlations rather than as differences of orthogonally-polarized fluxes. As a corollary, traditional polarization modulators may not be the cure-alls they are for single-telescope polarimetry. Polarization effects in the Coudé train and delay lines spoil the accuracy of traditional quasi-scalar interferometers. An alternative optical architecture is proposed, using traditional (i.e. single-beam) optical polarimetry in the correlator, but 'radio-type' transfer of light from telescope foci to correlator. Such a fundamental solution can eliminate errors due to inclined mirrors (phase shifts and added polarization). The architecture enables full-Stokes polarimetry at the resolution of the interferometer, but also a 'no-polarization-desired' mode which does not necessarily involve loss of signal-to-noise ratio and yet is free from polarization-induced errors of photometry. Existing polarization components permit a very wide instantaneous bandwidth.