Abstract

A new division-of-amplitude photopolarimeter¹ with no moving parts or modulators is described that employs the conical diffraction of light from a grating which is set for oblique incidence with the grating lines inclined with respect to the plane of incidence, Fig. 1. The grating G splits the incident light beam, whose state of polarization is to be measured, into four or more beams that are intercepted by linear photodetectors D_m (m = 0, 1, 2, …). This produces four or more signals i_m that represent multiple projections of the unknown Stokes vector S. S is reconstructed from its projections by matrix inversion. We have built a prototype photopolarimeter of this type using an Al-coated, 600-grooves/mm, holographic grating set at 65° angle of incidence with the grooves oriented at 45° with respect to the plane of incidence, and a 633-nm He-Ne laser as the light source. This novel photopolarimeter has been calibrated and tested, with and without the linear polarizers P_m in front of the photodetectors, using the same procedures recently established for the four-detector photopolarimeter^2,3 . This polarization-analysis scheme has several advantages and degrees of flexibility. In particular, it can be adapted using detector arrays so as to perform time-resolved spectropolarimetry.

© 1992 Optical Society of America