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Classical polarimetry with a twist: a compact, geometric approach



William Sparks, Thomas A. Germer, Rebecca M. Sparks


We present an approach to classical polarimetry which requires no moving parts, is compact and robust, and which encodes the complete polarization information on a single data frame, accomplished by replacing the rotation of components such as wave plates with position along a spatial axis. We demonstrate the concept with a polarimeter having a quarter wave plate whose fast axis direction changes with location along one axis of a 2D data frame in conjunction with a fixed-direction polarization analyzer, analogous to a classical rotating quarter wave plate polarimeter. The full set of Stokes parameters is obtained, with maximal sensitivity to circular polarization Stokes V if a quarter wave retarder is used. Linear and circular polarization terms are encoded with different spatial carrier frequencies which minimizes cross-talk. Other rotating component polarimeters lend themselves to the approach. Since the polarization modulation spatial frequencies do not change greatly, if at all, with wavelength such devices are close to achromatic, facilitating designs for both spectropolarimetry and polarimetric imaging. Since the polarimetric information is acquired in a single observation, transient or moving targets are accessible, loss of precision due to sequential data acquisition is avoided, and moving parts are not required.
Publications of the Astronomical Society of the Pacific


polarization, Stokes vector
Created May 22, 2019, Updated January 27, 2020