Broadband aperiodic Mo/Si multilayer polarization elements for EUV region

Broadband Mo/Si multilayer polarization optical elements were developed for the extreme ultraviolet (EUV) region, including a reflective analyzer and a transmission phase retarder. These multilayers were designed by a combined analytical/numerical method based on an aperiodic stack. Then these aperiodic multilayers were fabricated using direct-current magnetron sputtering technology. The multilayer structures were measured by an X-ray Diffractometer (XRD) working at the Cu-Kα line, and the polarization response was characterized by the polarimeter on the UE56/1-PGM1 beamline at BESSY-II, in Berlin. The measured s-polarized reflectivity is higher than 15% over the 13-19 nm wavelength range, and nearly constant s-reflectivity, up to 37%, is observed over the 15-17 nm wavelength range. Furthermore, these aperiodic multilayers show high s-reflectivity and polarization over a wide angular range at fixed wavelength. The measured phase shift is 41.7° over the 13.8-15.5 nm wavelength range. Using an aperiodic transmission phase retarder and a reflection analyzer, a complete broadband polarization analysis system was developed. The polarization properties of the synchrotron radiation from the beamline UE56/1 PGM1 at BESSY-II were systematically characterized in the 12.7-15.5 nm wavelength range by this newly developed broadband polarization analysis system. This kind of broadband multilayer polarizing elements can be used in EUV polarization measurements and will greatly simplify experimental arrangements.