Polarizing and non-polarizing mirrors in far UV for the Hydrogen Lyman-α radiation (λ = 121.6 nm)

Laboratoire Charles Fabry de l’Institut d’Optique, CNRS et Univ. Paris-Sud, 2 Av. Augustin Fresnel, RD 128, 91127 Palaiseau Cedex, France

Abstract

We demonstrate the feasibility of efficient polarizing and non-polarizing mirrors at λ = 121.6 nm designed within the framework of the Lyman α Lyot Coronograph Imager project. We have designed, realized and characterized such mirrors. Optical constants of the materials involved in the thin film coatings are determined experimentally. Reflectivity measurements in the VUV wavelength domain have been performed at PTB (Synchrotron at BESSY II, Berlin). A s-polarized reflectivity R_s as high as 68% is experimentally obtained with a coating made of a Fabry-Pérot resonator. To our knowledge this value is the highest ever reported for a polarizing mirror at this wavelength.