We have developed semi-transparent multilayer polarizers for polarimetry or ellipsometry in the soft x-ray region. We have studied the fabrication processes to achieve a flat and smooth freestanding reflection surface for high-performance semi-transparent multilayer beam-splitters, mainly the stress control of Mo/Si multilayer films and the surface roughness of the support membrane. In this work, we verified that these processes can be applicable to fabricate not only beam-splitters but also polarizers with high reproducibility. The flatness of 1.1 nm (rms) was obtained in the active area of a 11 mm square semi-transparent multilayer polarizer. The measured reflectivity and transmittance rates for s-polarization using synchrotron radiation were 45.3% and 5.6%, respectively, at a wavelength of 13.9 nm. We estimated the polarization characteristics by calculating its relative reflectivity, relative transmittance and phase shift for polarization experiments. As a result of the calculation, we verified that the fabricated semi-transparent multilayer polarizers can be adequately used as a polarizer with polarizance of 69.5% and high throughput of 28.9%, or as a phase shifter of 68 degrees with equal transmission ratio and high throughput of 4.9% for x-ray polarimetry or ellipsometry.
|