21 February 2003 Polarization and optical aperture synthesis: the problem and a solution
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Abstract
Light is not a scalar wave. We only get away with treating it as such when the degree of polarization is very low. This condition often holds for seeing-limited single telescopes, but becomes less likely at spatial resolutions typical for interferometers. 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. 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 (i.e. 2 clean, fully-polarized, signals from each telescope). 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 (e.g. 0.3 to > 1 μm, matching CCD or STJ detectors).
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jaap Tinbergen, Jaap Tinbergen, } "Polarization and optical aperture synthesis: the problem and a solution", Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); doi: 10.1117/12.457022; https://doi.org/10.1117/12.457022
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