Optical and structural characterization of reflective quarter wave plates for EUV range

Abstract

The high demand to understand the optical, electronic, and structure properties of materials has fostered to extend the investigation down to shorter wavelengths in the far ultraviolet (FUV) and extreme ultraviolet (EUV) range. This has pushed scientists to investigate and design new optical tools as wave retarder (QWR) which, coupled with other techniques, can provide valuable information about physical, like magnetic and optical properties of materials. We have designed and studied an EUV polarimetric apparatus based on multilayer structures as QWR with a protective capping layer to avoid oxidation and contamination to improve stability and reflectivity efficiency. This device works within a suitably wide spectral range (88-160 nm) where some important spectral emission lines are as the hydrogen Lyman alpha 121.6 and Oxygen VI (103.2 nm) lines. Such design could be particularly useful as analytical tools in EUV-ellipsometry field. The system can be a relatively simple alternative to Large Scale Facilities and can be applied to test optical components by deriving their efficiency and their phase effect, i.e. determining the Mueller Matrix terms, and even to the analysis of optical surface and interface properties of thin films. In addition, the phase retarder element could be used in other experimental applications for generating EUV radiation beams of suitable polarization or for their characterization.