Elliptical-polarization analyses of synchrotron radiation in the 5–80-eV region with a reflection polarimeter

Abstract

The Stokes parameters, which completely represent the polarization state of light, have been measured in the 5–80-eV energy region for synchrotron-radiation beams on the VUV to soft X-ray beamlines at the Photon Factory. Various states of polarization were produced for the emerging beam by deflecting the incoming beam vertically with respect to the entrance slit of the monochromator with a premirror of the beamline. The resultant beam was polarization-analyzed using a polarimeter comprising two triple-reflection polarizers. Increasing the beam-deflection angle was found to result in a change in the polarization state from predominantly horizontal linear polarization to elliptical polarization. This procedure could be used both to produce and to verify circular polarization with | P c| ≳ 80% in the energy range 60–80 eV, which could be immediately applied to MCD experiments. Unpolarized light could clearly be distinguished from circularly polarized light. The unpolarized component was found to become larger with increasing energy on a soft X-ray beamline; this was shown to be mainly due to scattering by beamline optical elements.