Optical components for polarization analysis of soft x-ray radiation

摘要

An instrument for measuring polarization typically consists of a phase shifter and a linear polarizer. Up to 600 eV, periodic multilayer structures can be used for this purpose. They consist of alternating layers of two materials, one of which has an absorption edge in the photon energy region of interest. The phase shift of the transmitted beam and the intensity of the reflected beam show maxima at energies just below the edge. Phase shifters on 100 nm thick Si$-3$/N$-4$/ membranes and linear polarizers on Si wafers have been made by DC magnetron sputter deposition. The polarizers were designed to work at the Brewster angle, where only s-polarized radiation is reflected. The corresponding multilayer period decreases from 8.5 nm at 100 eV to 1.4 nm at 600 eV. A reflectance of 6.8% was obtained at 512 eV for 150(V/Ni). In order to extend polarization measurements into the 1 keV region, the use of magnetic effects like magnetic circular dichroism (MCD) is being explored. This effect has been measured in Co/C and FeCoV/Ti transmission multilayers close to the L$-2,3$/ edges of Co and Fe.