Wedged double Wollaston, a device for single shot polarimetric measurements

Simultaneous measurements of the polarized flux at angles 0, 45, 90 and 135 degrees can be performed by inserting a simple combination of two Wollaston prisms and two wedges (cf. Fig. 1) in the pupil plane of a camera/spectrometer multimode astronomical instrument. The first three elements of the Stokes vector can be therefore determined from data taken at the same time and without any need of rotating plates or other moving elements which could be difficult to incorporate in multimode astronomical instruments. This paper describes the working principles of the wedged double Wollaston and presents detailed parameters for prism combinations optimized for imaging–polarimetry and spectro–polarimetry at "visual" (0.3 - 1.0 μm) and near IR (1.0-2.5 μm) wavelengths. The devices described here could significantly simplify the implementation of imaging and spectro–polarimetric modes in astronomical multimode focal reducers.